The appendages of the body are reduced to branchiae, present in certain forms. A clitellum is present.
It has been shown by C. Janet (1889), from careful studies of the musculature, that the greater part of the head-capsule is built up of the four anterior head-segments, the hindmost of which has the mandibles for its appendages, and this conclusion is in the main supported by the recent work on the head skeleton of J.
The appendages show various types of form and structure corresponding to different functions.
Lacuna, foot with two posterior appendages, marine, entirely aquatic. Cremnoconchus, entirely aerial, Indian.
The coenosarc may consist of a single elongated tube or stolon, forming the stem or axis of the cormus on which, usually, the appendages are arranged in groups termed cormidia; or it may take the form of a compact mass of ramifying, anastomosing tubes, in which case the cormus as a whole has a compact form and cormidia are not distinguishable.
The cormus is always differentiated into two parts; an upper portion termed the nectosome, in which the appendages are locomotor or hydrostatic in function, that is to say, serve for swimming or floating; and a lower portion termed the siphosome, bearing appendages which are nutritive, reproductive or simply protective in function.
Besides the three types of individual above mentioned, there are other appendages of hydroid colonies, of which the individuality is doubtful.
A typical Siphonophore is a stock or cormus consisting of a number of appendages placed in organic connexion with one another by means of a coenosarc. The coenosarc does not differ in structure from that already described in colonial Hydrozoa.
Divergent views have been held by different authors both as regards the nature of the cormus as a whole, and as regards the homologies of the different types of appendages borne by it.
The general theories of Siphonophoran morphology are discussed below, but in enumerating the various types of appendages it is convenient to discuss their morphological interpretation, at the same time.
In the siphosome the following types of appendages occur: I.
The ersaeome (Calycophorida), made up of the same appendages as the preceding type but with the addition of a nectocalyx; when free termed Ersaea.
Siphons or nutritive appendages, from which the order takes its.
Gonostyles, appendages which produce by budding medusae or gonophores, like the blastostyles of a hydroid colony.
The various types of appendages described in the foregoing may be arranged in groups termed cormidia.
Thus from the original planula three appendages are, as it were, budded off, while the planula itself mostly gives rise to coenosarc, just as in some hydroids the planula is converted chiefly into hydrorhiza.
In the first place the cormus has been regarded as a single individual and its appendages as organs.
dividual; it is still possible to compare appendages with parts of an individual which have become separated from one another } by a process of " dislocation of organs."
The Siphonula produced buds on the manubrium, as many Anthomedusae are known to do, and these by reduction or dislocation of parts gave rise to the various appendages of the colony.
70); no nectocalyces or bracts; appendages all on the lower side of the pneumatophore arising from a compact coenosarc, and consisting of a central After C. Gegenbaur.
The second type of differentiation is that between supporting axis and assimilating appendages.
The cells of the axis are commonly stouter and have much less chlorophyll than those of the appendages (Draparnaldia).
of supporting axes from assimilating appendages, and as the body increases in size and becomes a solid mass of cells or interwoven threads, a corresponding differentiation of a superficial assimilative system from the deep-lying parts.
2d, 3 c) is always "free," the legs, wings and other appendages not being 1 Instar is a convenient term suggested by D.
Russia has no oceanic possessions; her islands are all appendages of the mainland to which they belong.
In the Orthorrhapha, in the pupae of which the appendages of the perfect insect are usually visible, the pupa-case generally splits in a straight line down the back near the cephalic end; in front of this longitudinal cleft there may be a small transverse one, the two together forming a T-shaped fissure.
Where locomotive appendages (the parapodia of the Polychaeta) exist, they are never jointed, as always in the Arthropoda; nor are they modified anteriorly to form jaws, as in that group.
Appendages of body re „ duced to branchiae, present only in four species, and - - to the ventral copulatory 32 appendages of Alma and Criodrilus.
An epipodium bearing three pairs of tentacles and an operculigerous lobe with two appendages; inhabitants of the Sargasso weed.
Mantle with two posterior appendages; ctenidium large and capable of protrusion from pallial cavity.
Shell spiral; four cephalic tentacles; eyes absent; two pedal appendages.
Foot broad, with two slender posterior appendages; operculum unguiculate.
Head much flattened and wide, with eyes on sides; foot broad; siphon with internal appendages.
m, Midgut, with its hepatic appendages h, all of which are not figured.
No buccal appendages or suckers; a very long evaginable proboscis; a quadriradiate terminal branchia.
of any kind; a short evaginable pharynx, bearing paired conical buccal appendages or " cephalocones."
No branchia; two long and branched buccal appendages.
Dorsal respiratory appendages frequently present.
Usually two rows of ramified dorsal appendages.
No anterior tentacles, and no dorsal appendages; body laterally compressed, transparent; pelagic. Phyllirhoe.
Head broad, surrounded by a funnel-shaped velum or hood; no radula; dorsal appendages foliaceous.
Anterior tentacles forming a scalloped frontal veil; dorsal appendages and tentacles similarly ramified.
Dorsum furnished on either side with papillae, at the base of which are ramified appendages.
Body elongated; visceral mass marked off from foot posteriorly; dorsal appendages absent, or reduced to a single pair; spicules in the integument.
Anterior tentacles in the form of a digging shield; mantle without appendages, but respiratory papillae beneath the mantle-border.
The head of an insect carries usually four pairs of conspicuous appendages - feelers, mandibles and two pairs of maxillae, so that the presence of four primitive somites is immediately evident.
The compound eyes of insects resemble so closely the similar organs in Crustaceans that there can hardly be reasonable doubt of their homology, and the primitively appendicular nature of the eyes in the latter class suggests that in the Hexapoda also they represent the appendages of an anterior (protocerebral) segment.
The maxillae of the hinder pair become more or less fused together to form a " lower lip " or labium, and the segment of these appendages is, in some insects, only imperfectly united with the head-capsule.
Paired processes on the eighth and ninth abdominal segments may be specialized as external organs of reproduction, but these are probably not appendages.
It does not appear to represent a pair of appendages, but the maxillulae of the Aptera become closely associated with it.
Smaller appendages (such as the stylets of male cockroaches) may be carried on the ninth segment.
The labrum and clypeus are developed as a single prolongation of the oral piece, not as a pair of appendages.
The antennal segment apparently entirely disappears, with the exception of a pair of appendages it bears; these become the antennae; it is possible that the original segment, or some part of it, may even become a portion of the actual antennae.
The intercalary segment has no appendages, nor rudiments thereof, except, according to H.
Comstock and C. Kochi believe that the labrum belongs to it,, The appendages of the posterior three or trophal segments become the parts of the mouth.
The appendages of the two maxillary segments arise as treble instead of single projections, thus differing from other appendages.
From these facts it appears that the anterior three divisions of the head differ strongly from the posterior three, which greatly resemble thoracic segments; hence it has been thought possible that the anterior divisions may represent a primitive head, to which three segments and their leg-like appendages were subsequently added to form the head as it now exists.
Great difference of opinion exists as to the hypopharynx, which has even been thought to represent a distinct segment, or the pair of appendages of a distinct segment.
Though the T hx, thoracic segments bear the wings, no trace of these appendages exists till the close of the embryonic life, 8 `' nor even, in many cases, till much later.
s Abdominal Segments and i Appendages.
The appendages of the abdomen are called cerci, stylets and gonapophyses.
Difference of opinion as to the nature of the abdominal appendages pre vails.
The neuromeres are shown in Arabic, the appendages in Roman numerals.
The air-tubes, like the food-canal, are formed by invaginations of the ectoderm, which arise close to the developing appendages, the rudimentary spiracles appearing soon after the budding limbs.
21, d) - such as may be noticed in the majority of the Lepidoptera - whose appendages are closely and immovably pressed to the body by a general hardening and fusion of the cuticle.
Primitively (?) wingless Hexapods with cumacean mandibles, distinct maxillulae, and locomotor abdominal appendages.
Thysanura (Bristle-tails): with ten abdominal segments; number of abdominal appendages variable.
Collembola (Spring-tails): with six abdominal segments; appendages of the first forming an adherent ventral tube, those of the third a minute " catch," those of the fourth (fused basally) a " spring."
No locomotor abdominal appendages.
No locomotor abdominal appendages (except in certain larvae).
We may conclude, therefore, that they were preceded, in Cambrian times or earlier, by Arthropods possessing well developed appendages on all the trunk-segments.
Berlese, Gli Insetti (Milan, 1906), &c. (Extensive bibliographies will be found in several of the above.) Head and Appendages.
Abdomen and Appendages.
SPIDERS, the common English name of Arachnida of the order Araneae, resembling the Pedipalpi in many structural points, but differing from them as well as from all other Arachnida in retaining short abdominal appendages known from their silk-manipulating function as spinnerets or spinning mamillae, with which are associated silk glands.
There are no exterior appendages of any kind.
Again, the adult Pentastomum shows no trace of appendages, unless the two pairs of chitinous hooks are to be regarded as the vestiges of jaws or ambulatory limbs.
Hard by immense catacombs and columbaria have been opened which may have been appendages of the temple.
Interior of dorsal valve, showing muscular impressions and labial appendages.
In the Rhynchonellidae there are two short slender curved laminae, while in many genera and even families, such as the Productidae, Strophomenidae, Lingulidae, Discinidae, &c., there exists no calcified support for the labial appendages.
Interior of dorsal valve, to show the position of the labial appendages.
d, h, Brachial appendages.
The evidence of the exact equivalence of the segmentation and appendages of Limulus and Scorpio, and of a number of remarkable points of agreement in structure, was furnished by Ray Lankester in an article published in 1881 (" Limulus an Arachnid," Quart.
(From Lankester.) to possess only five pairs of anterior or prosomatic appendages.
The various comparisons previously made between the structure of Limulus and the Eurypterines on the one hand, and that of a typical Arachnid, such as Scorpio, on the other, had been vitiated by erroneous notions as to the origin of the nerves supplying the anterior appendages of Limulus (which were finally removed by Alphonse Milne-Edwards in his beautiful memoir (6) on the structure of that animal), and secondly by the erroneous identification of the double sternal plates of Limulus, called " chilaria," by Owen, with a pair of appendages (7).
14 and 15), each carrying a pair of plate-like appendages in both Limulus and Scorpio.
The first pair of foliaceous appendages in each animal is the genital operculum; beneath it are found the openings of the genital ducts.
The second pair of mesosomatic appendages in Scorpio are known as the " pectens."
The next four pairs of appendages (completing the mesosomatic series of six) consist, in both Scorpio and Limulus, of a base carrying each 130 to 150 blood-holding, leaf-like plates, lying on one another like the leaves of a book.
There is no doubt that these are parapodial or limb appendages, carrying numerous imbricated secondary processes, and therefore comparable in essential structure to the leaf-bearing plates of the second meso somatic somite of Limulus.
They have remained unenclosed and projecting on the surface of the body, as once were the appendages of the four following somites.
61° tory organs of those creatures in the con-;...« dition of projecting appendages serving =?.?
Perhaps the most important general agreement of Scorpio compared with Limulus and the Eurypterines is the division of the body into the three regions (or tagmata) - prosoma, mesosoma and metasoma - each consisting of six segments, the prosoma having leg-like appendages, the mesosoma having foliaceous appendages, and the metasoma being destitute of appendages.
In the case of Scorpio this segment is indicated in the embryo by the presence of a pair of rudimentary appendages, carried by a well-marked somite.
As in Limulus, so in Scorpio, this unexpected somite and its appendages disappear in the course of development.
But it is necessary to remember, in the light of recent discoveries, that the sixth prosomatic pair of appendages is carried on the seventh somite of the whole series, there being two prosthomeres or somites in front of the mouth, the first carrying the eyes, the second the chelicerae; also that the first mesosomatic or genital somite is not the seventh or even the eighth of the whole series of somites which have been historically present, 1 See the article Arthropoda for the use of the term " prosthomere."
We shall, therefore, ignoring the ocular somite, speak of the first, second, third, fourth, fifth and sixth legbearing somites of the prosoma, and indicate the appendages by the Roman numerals, I, II, III, IV, V, VI, and whilst ignoring the praegenital somite we shall speak of the first, second, third, &c., somite of the mesosoma or opisthosoma (united mesosoma and metasoma) and indicate them by the Arabic numerals.
There are a number of other important points of structure besides those referring to the somites and appendages in which Limulus agrees with Scorpio or other Arachnida and differs from other Arthro- '11'1 poda.
The first of these has, in Arachnids as in other Arthropods, its pair of appendages represented by the eyes.
The second has for its pair of appendages the small pair of limbs which in all living Arachnids is either chelate or retrovert (as in spiders), and is known as the chelicerae.
The cerebral mass is in Limulus more easily separated by dissection as a median lobe distinct from the laterally placed ganglia of the cheliceral somite than is the case in Scorpio, but the relations are practically the same in the two forms. Formerly it was supposed that in Limulus both the chelicerae and the next following pair of appendages were prosthomerous, as in Crustacea, but the dissections of Alphonse Milne-Edwards (6) demonstrated VI FIG.
Limulus thus agrees with Scorpio and differs from the Crustacea, in which there are three prosthomeres - one ocular and two carrying palpiform appendages.
- The prosomatic appendages of Limulus polyphemus (right) and Scorpio (left), Palamnaeus indus compared.
The corresponding appendages are marked with the same Roman numeral.
(From Lankester, loc. cit.) palpiform appendages.
--Diagrams of the meta-sternite st, who showed that with genital operculum op, and the first lamellithe statements of gerous pair of appendages ga, with uniting von Graber were sternal element st of Scorpio (left) and Limulus erroneous, and (right).
- The first three pairs of mesosomatic appendages of Scorpio and Limulus compared.
- The remaining three pairs of mesosomatic appendages of Scorpio and Limulus.
In Limulus small entosternites are found in each somite of the appendage-bearing mesosoma, and we find in Scorpio, in the only somite of the mesosoma which has a welldeveloped pair of appendages, that of the pectens, a small entosternite with ten pairs of muscles inserted into it.
- Embryo of scorpion, ventral view showing somites and appendages.
abp 4 to abp', Rudiments of the four appendages which carry the pulmonary lamellae.
The praegenital somite, VII PrG, is still present, but has lost its rudimentary appendages; go, the genital operculum, left half; Km, the left pecten; abp 4 to abp 7, the rudimentary appendages of the lung-sacs.
br' to br', Branchial appendages.
They differ from the Crustacea in that they have only a single pair of prae-oral appendages, the second pair being definitely developed as mandibles.
The fact that the single pair of prae-oral appendages of trilobites, known only as yet in one genus, is in that particular case a pair of uni-ramose antennae - does not render the association of trilobites and Arachnids improbable.
Although the prae-oral pair of appendages in the higher Arachnida is usually chelate, it is not always so; in spiders it is not so; nor in many Acari.
- Euarthropoda having two prosthomeres (somites which have passed from a post-oral to a prae-oral position), the appendages of the first represented by eyes, of the second by solitary rams which are rarely antenniform, more usually chelate.
Little is known of the form of the appendages in the lowest archaic Arachnida, but the tendency of those of the prosomatic somites has been (as in the Crustacea) to pass from a generalized bi-ramose or multi-ramose form to, that of uni-ramose antennae, chelae and walking legs.
The single pair of palpiform appendages in front of the mouth has been found in one instance to be antenniform, whilst the numerous post-oral appendages in the same genus were bi-ramose.
The members of this group, whilst resembling the lower Crustacea (as all lower groups of a branching genealogical tree must do), differ from them essentially in that the head exhibits only one prosthomere (in addition to the eye-bearing prosthomere) with palpiform appendages (as in all Arachnida) instead of two.
These plates may fuse, and yet the somites to which they belong may remain distinct, and each have its pair of appendages well developed.
(After Beecher.) ancestor of the grade) grouped in three regions of six - (a) the " prosoma " with palpiform appendages, (b) the " mesosoma " with plate-like appendages, and (c) the " metasoma " with suppressed FIG.
(From Zittel's Palaeontology.) (After Beecher.) appendages.
In living Arachnids, excepting the Pantopoda, it is either fused (with loss of its appendages) with the prosoma (Limulus, 1 Scorpio), after embryonic appearance, or is 1 Pocock suggests that the area marked vii.
Four pairs of appendages besides these are seen to belong to the cephalic tergum.
All the appendages are pediform and bi-ramose; all have a prominent gnathobase, and in all the exopodite carries a comb-like series of secondary processes.
This concentration and obliteration of somites, often accompanied by dislocation of important segmental structures (such as appendages and nerveganglia), may lead to highly developed specialization (individuation, H.
The seventh, and sometimes the eighth, leg-bearing somite is present and has its leg-like appendages fully developed.
- One of the Nymphonomorphous Pantopoda, Nymphon hispidum, showing the seven pairs of appendages I to 7; ab, the rudimentary opisthosoma; s, the mouth-bearing proboscis.
In certain derivative forms constituting the family Pallenidae, however, the appendages of the 2nd pair are either rudimentary or atrophied altogether.
- Appendages of the 2nd and 3rd pairs retained and developed, as in the more primitive types of Nymphonomorpha; but those of the 1st pair are either rudimentary, as in the Ascorhynchidae, or atrophied, as in the Colossendeidae.
- Derivative forms in which the reduction in number of the anterior appendages is carried farther than in the other orders, reaching its extreme in the Pycnogonidae, where the 1st and 2nd pairs are absent in both sexes, and the 3rd pair also are absent in the female.
In the same and other leading forms a pair of much-coiled glandular tubes, the coxal glands (coelomocoels in origin), is found with a duct opening on the coxa of the fifth pair of appendages of the prosoma.
Mesosomatic segments furnished with large plate-like appendages, the 1st pair acting as the genital operculum, the remaining pairs being provided with branchial lamellae fitted for breathing oxygen dissolved in water.
The mouth lying far back, so that the basal segments of all the prosomatic appendages, excepting those of the 1st pair, are capable of acting as masticatory organs.
Not freeswimming, none of the prosomatic appendages modified to act as paddles; segments of the mesosoma and metasoma (= opisthosoma) not more than ten in number, distinct or coalesced.
In none of them are the appendages known, but in the form of the two carapaces and the presence of free somites they are distinctly intermediate between Limulus and the Trilobitae.
- Free-swimming forms, with the appendages of the 6th or 5th and 6th pairs flattened or lengthened to act as oars; segments of mesosoma and metasoma (= opisthosoma), twelve in number.
operc, the fused first pair of mesosomatic appendages forming the genital operculum.
The dorsal aspect is presented showing the prosomatic shield with paired compound eyes and the prosomatic appendages II.
The small first pair of appendages is concealed from view by the carapace.
(From Zittel's Textbook of Palaeontology, The Macmillan Co., New York, 1896.) Appendages of anterior pair very large and chelate.
Appendages of anterior pair minute and chelate.
There still appears to be some doubt whether in the sub-order Eurypteromorpha the first pair of prosomatic appendages (fig.
Though there are indications of lamelliform respiratory appendages on mesosomatic somites following that bearing the genital operculum, we cannot be said to have any proper knowledge as to such appendages, and further evidence with regard to them is much to be desired.
In primitive forms the respiratory lamellae of the appendages of the 3rd, 4th, 5th and 6th, or of the 1st and 2nd mesosomatic somites are sunk beneath the surface of the body, and become adapted to breathe atmospheric oxygen, forming the leaves of the so-called lung-books.
The appendages of the mesosoma generally suppressed; in the more primitive forms one or two pairs may be retained as organs subservient to reproduction or silkspinning.
Mouth situated more forwards than in Delobranchia, no share in mastication being taken by the basal segments of the 5th and 6th pairs of prosomatic appendages.
- The primitive distinction between the mesosoma and the metasoma retained, the latter consisting of six somites and the former of six somites in the adult, each of which is furnished during growth with a pair of appendages.
The appendages of the 1st and 2nd mesosomatic somites persisting as the genital operculum and pectones respectively, those of the 3rd, 4th, 5th and 6th somites (?
- Prosoma covered by a single dorsal shield, bearing typically median and lateral eyes; its sternal elements reduced to a single plate lodged between or behind the basal segments of the 5th and 6th pairs of appendages.
Appendages of 1st pair.tri-segmented, chelate; of 2nd pair chelate, with their basal segments subserving mastication; of 3rd, 4th, 5th and 6th pairs similar in form and function, except that in recent and Carboniferous forms the basal segments of the 3rd and 4th are provided with sterno-coxal (maxillary) lobes, those of the 4th pair meeting in the middle line and underlying the mouth.
- The 3rd, 4th, 5th and 6th pairs of appendages short, stout, tapering, the segments about as wide as long, except the apical, which is distally slender, pointed, slightly curved, and without distinct movable claws.
- The 3rd, 4th, 5th and 6th pairs of appendages slender, not evenly tapering, the segments longer than wide; the apical segment short, distally truncate, and provided with a pair of movable claws.
The fifth pair of prosomatic appendages is used by these scorpions when burrowing, to kick back the sand as the burrow is excavated by the great chelae.
- The primitive distinction between the mesosoma and the metasoma wholly or almost wholly obliterated, the two regions uniting to form an opisthosoma, which never consists of more than twelve somites and never bears appendages or breathing-organs behind the 4th somite.
The appendages of the 2nd somite of the opisthosoma absent, rarely minute and budlike (some Amblypygi), never pectiniform.
- Appendages of 1st pair bisegmented, without poison gland; of 2nd pair prehensile, their basal segments underlying the proboscis, and furnished with sterno 1 to i 1, Somites of the opisthosoma (mesosoma plus metasoma).
coxal (maxillary) process, the apical segment tipped with a single movable or immovable claw; appendages of 3rd pair different from the remainder, tactile in function, with at least the apical segment many-jointed and clawless.
Opisthosoma consisting of eleven somites, almost wholly without visible appendages.
Appendages of 2nd pair with their basal segments united in the middle line and incapable of lateral movement; appendages of 3rd pair with only the apical segment many-jointed.
Appendages of 2nd pair folding in a horizontal plane, completely chelate, the claw immovably united to the sixth segment.
Appendages of 2nd pair folding in a vertical plane, not chelate, the claw long and movable.
- Schizomus crassicaudatus, a Tartarid Pedipalp. Dorsal view of a male with the appendages cut short.
The prosomatic appendages.
Sternal area broad, with prosternal, two mesosternal, and metasternal plates, the prosternum projecting forwards beneath the coxae of the 2nd pair of appendages.
Appendages of 2nd pair folding in a horizontal plane; their basal segments n From Lankester, Q.
Ventral view of a female with the appendages cut short near the base.
(Original drawing by Pocock.) freely movable; claw free or fused; basal segments of 4th and 5th pairs widely separated by the sternal area; appendages of 3rd pair with all the segments except the proximal three, forming a manyjointed flagellum.
II to VI, the prosomatic appendages, the first being concealed (see fig.
(Original as preceding.) appendages on the sternum of the 3rd somite.
I to VI, the prosomatic appendages; 4, 5, 6, the fourth, fifth and sixth tergites of the opisthosoma.
Appendages of 1st pair have two segments, as in Pedipalpi, but are furnished with poison gland, and are retroverts.
Appendages of 2nd pair not underlying the mouth, but freely movable and, except in primitive forms, furnished with a maxillary lobe; the rest of the limb like the legs, tipped with a single claw and quite unmodified (except in a').
Remaining pairs of appendages similar in form and function, each tipped with two or three claws.
Opisthosoma when segmented showing the same number of somites as in the Pedipalpi; usually unsegmented, the prae-genital somite constricted to form the waist; the appendages of its 3rd and 4th somites retained as spinning mammillae.
Ventral view with the prosomatic appendages cut short excepting the chelicerae (I) whose sharp retroverts are seen.
In front of it the narrow waist is formed by the soft sternal area of the praegenital somite; 2, the sternite of the 2 second opisthosomatic somite covering the posterior pair of lung-sacs; and 4, the spinning appendages (limbs) of the opisthosoma; a, inner, b, outer ramus of the appendage; I I, sternite of the eleventh --
- The plane of the articulation of the appendages of the 1st pair to the prosoma (the retrovert) vertical, the basal segment pro jecting straight forwards at its proximal end, the t raegcn - distal segment or fang closing backwards in a direction subparallel to the long axis of the body.
- The plane of the articulation of the appendages of the 1st pair to the prosoma horizontal, the basal segment projecting ver tically downwards, at least at its proximal end, the distal segment II III IV V VI? ?.I?!1?1UII!119N; / I II III IV V VI 2 3 4 II FIG.
to VI, Appendages of the prosoma cut off at the base.
The " retrovert " or bent-back first pair of appendages is provided with a poison gland opening on the fang or terminal segment.
Appendages of 1st pair consisting of three segments, completely chelate, without poison gland; of 2nd pair slender, leg-like, tipped with three claws, the basal segment without sterno-coxal process taking no share in mastication, and widely separated from its fellow of the opposite side; 3rd, 4th, 5th and 6th appendages similar in form to the 2nd and to each other.
Proboscis free, not supported from below by either the prosternum or the basal segments of the appendages of the 2nd pair.
A, Ventral view of prosoma and of anterior region of opistho soma with the appendages cut off near the base; a and b, B, Dorsal view.
I to VI, prosomatic appendages; i opisth, genital somite (first opisthosomatic somite).
C, Lateral view, I to VI, proprosternites; c, mesosternite; and d, metasternite of the somatic appendages; a,b,c, prosoma; f, ventral surface the three tergal plates of the of the prae-genital somite; prosoma; prae-gen, the prae g, sternite of the genital genital somite; 1 to 10, the somite (first opisthosomatic ten somites of the opisthosoma.
Rostrum free, not supported by either the prosternum or the basal segments of the appendages.
Appendages of 1st pair large, chelate, bisegmented, articulated to the sides of the head-shield; appendages of 2nd pair simple, pediform, with protrusible (?
Remaining pairs of appendages with their basal segments immovably fixed to the sternal surface, similar in form, the posterior three pairs furnished with two claws supported on long stalks; the basal segments of the 6th pair bearing five pairs of tactile sensory organs or malleoli.
Intromittent organ of male lodged on the dorsal side of the 1st pair of prosomatic appendages.) Families - Hexisopodidae (Hexisopus).
I to VI, The six pairs of prosomatic appendages.
The segmentation of the prosoma and the form of the appendages bear a homoplastic similarity to the head, pro-, meso-, and meta-thorax of a Hexapod with mandibles, maxillary palps and three pairs of walking legs; while the opistho io i e d c b o a S' S" 2 I VT V S IV III II I Opisthosoma Prosoma FIG.
plate correspondingrespectively S, Prosomatic tracheal aperture to appendages I, II, III, and between legs IV and V.
Appendages of the 1st FIG.
Ventral view with the appendages cut off at the base.
I to VI, Prosomatic appendages.
I to VI, Bases of the prosomatic appendages.
a, Lateral region of the cephalic plate to which the first pair of appendages are articulated.
c, Dorsal element of somites bearing third and fourth pairs of appendages.
d, Second plate of the prosoma with fifth pair of appendages.
I to VI, The prosomatic appendages.
The proportionately enormous chelae (chelicerae) of the first pair of appendages are not provided with poison glands; their bite is not venomous.
Appendages of 2nd pair very large and completely chelate, their basal segments meeting in the middle line, as in the Uropygi, and provided in front with membranous lip-like processes underlying the proboscis.
Appendages of the 3rd, 4th, 5th and 6th pairs similar in form and function, tipped with two claws, their basal segments in contact in the median ventral line.
- Dorsal plate of prosoma (carapace) narrowed in front; the appendages of the 1st pair small, much narrower, taken together, than the posterior border of the carapace.
Serrula on movable digit of appendages of 1st pair fixed throughout its length, and broader at its proximal than at its distal end; the immovable digit with an external process.
- Dorsal plate of prosoma scarcely narrowed in front; the appendages of the 1st pair large, not much narrower, taken together, than the posterior border of the carapace.
I to VI, Basal segments of the 2, 3, 10, The second, third and six prosomatic appendages.
The similarity of the form of their appendages to those of the scorpions suggests that they are a degenerate group derived from the latter, but the large size of the prae-genital somite in them would indicate a connexion with forms preceding the scorpions.
III to VI, The third, fourth, fifth followed by the opisthosoma of and sixth appendages of the four visible somites.
called hood) overhanging the E, Extremity of the fifth append first pair of appendages.
(Original drawing by Pocock and Pickard-Cambridge.) appendages of the 1st pair.
Appendages of 1st pair, bi-segmented, completely chelate.
Appendages of 2nd pair, with their basal segments uniting in the middle line below the mouth, weakly chelate at apex.
Appendages of 3rd, 4th, 5th and 6th pairs similar in form; their basal segments in contact in the middle line and immovably welded, except those of the 3rd pair, which have been pushed aside so that the bases of the 2nd and 4th pairs are in contact with each other.
I to VI, The six pairs of appendages of the prosoma, the last three cut short.
a, Visible hood overhanging the first pair of appendages.
Opisthosoma confluent throughout its breadth with the prosoma, with the dorsal plate of which its anterior tergal plates are more or less fused; at most ten opisthosomatic somites traceable; the generative aperture thrust far forwards between the basal segments of the 6th appendages.
Respiratory organs tracheal, opening by a pair of stigmata situated immediately behind the basal segments of the 6th pair of appendages on what is probably the sternum of the 2nd opisthosomatic somite and also in some cases upon the 5th segment of the legs.
Coxae of 4th, 5th and 6th appendages immovable.
Appendages of 2nd pair, strong, usually prehensile and spiny.
Orifice of coxal gland situated between the coxae of the 5th and 6th appendages.
Coxae of 3rd, 4th, 5th and 6th appendages movable 3 Prosoma 10 II d an FIG.
Extremity of the fifth pair of appendages of the female for comparison with that of the male E in fig.
Appendages of 2nd pair weak, pediform not prehensile.
Coxae of 5th and 6th, and usually also of 4th appendages immovable.
Appendages of 2nd pair weak, pediform, not prehensile.
,?, VI B, Ventral view of the prosoma and of the first somite of the opisthosoma, with the appendages I to VI cut off at the base; a, tracheal stigma; mx, maxillary processes of the coxae of the 3rd pair of appendages; g,genital aperture.
D, Lateral view of the 1st and 2nd pair of appendages.
E, Lateral view of the whole body and two 1st appendages, showing the fusion of the dorsal elements of the prosoma into a single plate, and of those of the opisthosoma into an imperfectly segmented plate continuous with that of the prosoma.
In the Phalangiotarbi the appendages resembled those of the Anthracomarti, except that the basal segments of the last four pairs were usually approximated in the middle line leaving a long and narrow sternal area between; and the carapace of the prosoma was unsegmented.
Tracheae typically opening by stigmata situated in the articular sockets (acetabula) of the 3rd, 4th, 5th and 6th pairs of appendages.
Tracheae opening by a pair of stigmata situated above and behind the base of the 4th or 5th or 6th pair of appendages.
Tracheae, except in the aquatic species in which they are atrophied, opening by a pair of stigmata situated close to or above the base of the appendages of the 1st pair (mandibles).
A, Lateral view with appendages III to VI removed; 1, plate covering the whole dorsal area, representing the fused tergal sclerites of the prosoma and opisthosoma; 2, similarly-formed ventral plate; 3, tracheal stigma.
B, Dorsal view of the same animal; II to VI, 2nd to 6th pairs of appendages.
The 1st pair of appendages both in this and in C are retracted.
To the average man there is a distinction between clothing and ornament, the first being regarded as that covering which satisfies the claims of modesty, the second as those appendages which satisfy the aesthetic sense.
Perithecium or "fruit" of the fungus with its curled appendages, X too.
The extraordinary variety of form and complication of structure exhibited by the appendages of the scolex are adaptations to fix FIG.
Apart from these characteristics, the most distinctive feature of earwigs is the presence at the end of the abdomen of a pair of pincers which are in reality modified appendages, known as cercopods, and represent the similar limbs of Japyx and the caudal feelers of Campodea and some other insects.
(2) The presence of variously formed scales on the body and its appendages: the head is clothed with scales, the thorax with hairs or scales, and the abdomen with either hairs or scales, or both; the legs and veins of the wings are always covered with scales, and the palpi are often (as in some Anophelinae) conspicuously scaly.
They are usually found in the alimentary canal or its appendages but occasionally work their way into the serous cavities, nervous system and blood vessels.
The most singular of the external appendages found in the Polyzoa are the avicularia and vibracula of the Cheilostomata.
keitloa, but the characters of these appendages are too variable for specific distinctions.
with the appendages not fixed to the body, as is the case in the pupa of most moths.
His forum and its numerous appendages were constructed on a magnificent scale.
These are light yellow in colour and in appearance resemble their mother, but with relatively larger appendages.
The primitive Artiodactyla thus probably had the typical number (44) of incisor, canine and molar teeth, brachyodont molars, conical odontoid process, four distinct toes on each foot, with metacarpal, metatarsal and all the tarsal bones distinct, and no frontal appendages.
No frontal appendages.
Geologically the Riouw and Lingga Islands are appendages of the Malay Peninsula, not of Sumatra.
it and its appendages were assigned to Lawrence Parsons, brother of Sir William Parsons, surveyor-general.
The Branchiopoda have a very variable number of body-segments, with or without a shield, simple or bivalved, and some of the postoral appendages normally branchial.
To these succeed eight pairs of foliaceous branchial appendages on the front division of the body, followed on the hind division by four pairs of powerful bifurcate swimming feet and two rudimentary pairs, the number, though not the nature, of these appendages being malacostracan.
This " leaf-footed " suborder has the appendages which follow the second maxillae variable in number, but all foliaceous and branchial.
In the long familiar Branchipus, Chirocephalus and Streptocephalus the males have frontal appendages, but these are wanting in the " brine-shrimp " Artemia, and the same want helps to distinguish Branchinecta (Verrill, 1869) from the old genus Branchipus.
By various modifications of their valves and appendages the creatures have become adapted for swimming, creeping, burrowing, or climbing, some of them combining two or more of these activities, for which their structure seems at the first glance little adapted.
The first legs, meaning thereby the sixth pair of appendages, are generally pediform and locomotive, but sometimes unjointed, acting as a kind of brushes to cleanse the furca, while in the Polycopidae they are entirely wanting.
Giesbrecht and Hansen have shown that the mouth-organs consist of mandibles, first and second maxillae and maxillipeds; and Claus himself relinquished his long-maintained hypothesis that the last two pairs were the separated exopods and endopods of a single pair of appendages.
Lialis burtoni, of similar size and distribution, has the hind-limbs reduced to very small, narrow appendages.
E, dorsal view of a male: a, lateral appendages; b, dorsal appendage.
Hudson in 1871 and found in numbers several times since, these appendages have acquired a new and quite special development.
Ploimoidaceae; subconical; corona bilobed; retractile foot absent or ciliated; motile appendages present in two families.
For many years only the dorsal surface of Trilobites was known, nothing having been ascertained of the ventral surface and appendages.
As in all Arachnida there is only a single pair of appendages in front of the mouth, and these were onebranched, long and filiform and acted as antennae.
Under the pygidium or caudal shield the appendages were much shortened, and their main branch consisted of broader and flatter segments than those of the preceding limbs.
Such was the structure of the appendages in Trilobites belonging to the genus Triarthrus; but considering the great structural differences that obtain between Triarthrus and many other genera, it would be rash to assume that there were not corresponding differences in the structure of the limbs.
In external form Trilobites are not unlike Isopod Crustaceans, especially the terrestrial species commonly called "woodlice"; and until the nature of their appendages was known, it was thought by some authorities that the two groups might be related.
Both British breeds, as well as those from abroad, are frequently ornamented with two tassel-like appendages, hanging near together under the throat.
jaws under Hexapoda); in the presence of a large number of excretory (Malpighian) tubes; in the firm texture of the forewings; in the presence of appendages (cerci) on the tenth abdominal segment; and in the absence of a metamorphosis, the young insect after hatching closely resembling the parent.
Our selected divisions relate only to the High Alps between the Col de Tenda and the route over the Radstddter Tauern, while in each of the 18 subdivisions the less elevated outlying peaks are regarded as appendages of the higher group within the topographical limits of which they rise.
Usually each tube is provided with caecal appendages on its proximal portion, and these serve as vesiculae seminales, while the distal portion is enlarged and glandular and secretes the egg-shell.
The form of the fruit body, the difference and the nature of special outgrowths upon it - the appendages - are characteristic of the various genera.
The receptacle ends above in appendages, each consisting of one or a few cells, some of which are the male organs, others the female organs, and others again may be barren hairs.
When a simple leaf is divided at the base into two leaf-like appendages, it is called auriculate.
The arrangement of the leaves on the axis and its appendages is called phyllotaxis.
These scales or protective appendages of the bud consist either of FIG.
In plants of warm climates the buds have often no protective appendages, and are then said to be naked.
M, Chara sp., axis with leaf-like appendages and a branch.
Attached to the bottom of pools series of the Confervales, the thallus consists of filaments branched by means of rhizoids, the thallus of Characeae grows upwards by or unbranched, attached at one extremity, and growing almost means of an apical cell, giving off whorled appendages at regular wholly at the free end.
The appendages have a limited growth; but in conphoraceae.
The antheridia and oogonia are formed at the nodes of the appendages.
Constantinea sp., with flattened leaf-like appendages.
Chrysymenia uvaria, axis with swollen leaf-like appendages.
Another general, although not universal, characteristic of the Pecora is the presence of simple or complex appendages on the forehead commonly known as horns.
In a few existing species, such as the musk-deer and the water-deer, these appendages are absent, and they are likewise lacking in a large number of extinct members of the group, in fact in all the earlier ones.
2 Sivatherium there are two pairs of such appendages, of which the hinder are large and were probably covered during life either with skin or thin horn.
The above-mentioned four types of skull appendages are generally regarded as severally characteristic of as many family groups, namely the Giraffidae, Cervidae, Antilocapridae and Bovidae.
In the Giraffidae, which include not only giraffes (Giraffa) but also the okapi (Ocapia) and a number of extinct species from the Lower Pliocene Tertiary deposits of southern Europe, Asia and North Africa, the appendages on the skull are of type No.
The frontal appendages, when present, are confined (except in the case of the reindeer) to the males, and take the form of antlers, that is to say of type No.
From the presence of these well-marked antlers the skeleton would at first sight be set down as that of a small and primitive deer, conforming in regard to the structure of these appendages to the American type of the group. Mr W.
Either we must regard Merycodus as a deer which parallels the antelopes and the prongbuck in every detail of skeletal structure, or else, like the prongbuck, an antelope separated from the main stock at a date sufficiently early to have permitted the development of a distinct type of cranial appendages, namely, antlers in place of true horns.
On the latter view Merycodus, the prongbuck (Antilocapra) and the antelopes must be regarded as representing three branches from an original common stock, divergent as regards the structure of their cranial appendages, but parallel in other respects.
The animals thus associated, the Rotifera, Chaetopoda and Arthropoda, are composed of a larger or smaller number of hollow rings, each ring possessing typically a pair of hollow lateral appendages, moved by intrinsic muscles and penetrated by blood-spaces.
An excellent example of structures differentiated according to position is given by the appendages borne on the stem of an ordinary flowering plant-the one or two seed leaves; the stem leaves, which may or may not be differentiated into secondary sets; and the various floral organs borne at the apex of the stem or its lateral branches.
It has the same moderately long, plump body, with a low dorsal crest, the continuation of the membrane bordering the strongly compressed tail; a large thick head with small eyes without lids and with a large pendent upper lip; two pairs of well-developed limbs, with free digits; and above all, as the most characteristic feature, three large appendages on each side of the back of the head, fringed with filaments which, in their fullest development, remind one of black ostrich feathers.
2.--Head and Appendages of Honey-bee (Apis) (magnified sixteen times).
(a) letters made as upright as possible, and with few exceptions equal in height; (b) the majority of the letters constructed of vertical lines, with appendages attached mostly at the foot, occasionally at the foot and at the top, or (rarely) in the middle, but never at the top alone; (c) at the tops of the characters the ends of vertical lines, less frequently straight horizontal lines, still more rarely curves or the points of angles opening downwards, and quite exceptionally, in the symbol ma, two lines rising upwards.
In neither does the terminal segment or telson, whether large or obsolescent, whether articulated or coalescent, carry appendages, unless occasionally in fusion with itself.
Between the eyes and the tail-piece in all the orders nineteen segments are counted, the proof of a segment's existence depending on its separateness, complete or partial, or on a sutural indication, or else on the pair of appendages known to belong to it.
Of the corresponding pairs of appendages thirteen belong to the head and trunk, two pairs of antennae, one pair of mandibles, two pairs of maxillae, followed by three which may be all maxillipeds or may help to swell the number of trunk-legs to which the next five pairs belong.
Underlying the diversity of names and functions and countless varieties of shape, there is a common standard' to which the appendages in general can be referred.
In the rest of the appendages they may either be wanting or indistinguishable.
They agree with the true crabs in not having appendages (uropods) to the sixth segment of the pleon, the atrophy being complete in the Homolidae and Homolodromiidae, whereas in the Dromiidae and Dynomenidae a pair of small plates appear to be vestiges of these organs.
The second maxillipeds are developed into powerful prehensile organs, and the branchiae, instead of being connected with the appendages of head and trunk, are developed on the pleopods, appendages of the abdomen.
Normally the pleon carries six pairs of two-branched appendages, of which the first three are much articulated flexible swimming feet, the last three few-jointed comparatively indurated uropods.
In the companion tribes these appendages have normally seven joints, and always more than three.
i, Mn.; 4), with toothed apex and sub-apical grinding surface, like those of certain Crustacea; by the presence between the mandibles and maxillae of a pair of appendages (superlinguae or maxil ' x lulae), fig.
The cerci in Japyx are not, as usual, jointed feelers, but strong, curved appendages forming a forceps as in earwigs.
The third abdominal segment usually carries a pair of short appendages whose basal segments are fused together; this is the "catch" (fig.
2, 7), whose function is to hold in place the "spring," which is formed by the fourth pair of abdominal appendages - also with fused basal segments.
The fused basal segments of the appendages form the "manubrium" of the spring, which carries the two "dentes" (usually elongate II.
ii.-x, Appendages on 2nd to Toth abdominal segments.
It will be sufficient here to define them as Arthropoda for the most part of aquatic habits, having typically two pairs of antenniform appendages in front of the mouth and at least three pairs of post-oral limbs acting as jaws.
In its simplest form the exoskeleton of a typical somite is a ring of chitin defined from the rings in front and behind by areas of thinner integument forming moveable joints, and having a pair of appendages articulated to its ventral surface on either side of the middle line.
Others have regarded it as representing the fusion of a number of somites, and others again as a " median appendage " or as a pair of appendages fused.
- The Separated Somites and Appendages of the Common Lobster (Homarus gammarus).
T, telson, having the uropods or appendages of the last abdominal somite spread out on either side of it, forming the " tail-fan."
Even where a large number of the somites have fused, there is generally a marked change in the character of the appendages after the fifth pair, and since the integumental fold which forms the carapace seems to originate from this point, it is usual to take the fifth somite as the morphological limit of the cephalon throughout the class.
The three pairs of appendages present in the " nauplius " larva show certain peculiarities of structure and development which seem to place them in a different category from the other limbs, and there is some ground for regarding the three corresponding somites as constituting a " primary cephalon."
4), and the two regions are sharply distinguished by the character of their appendages.
14, third abdominal somite, with appendages or " swimmerets."
General Morphology of Appendages.
- Amid the great variety of forms assumed by the appendages of the Crustacea, it is possible to trace, more or less plainly, the modifications of a fundamental type consisting of a peduncle, the protopodite, bearing two branches, the endopodite and exopodite.
In the appendages near the mouth one or both of the protopodal segments may bear inwardly-turned processes, assisting in mastication and known as gnathobases.
leaf-like appendages of the Phyllo poda as nearer the original form from which the various modifications found in other groups have been derived.
The Phyllopoda are the only Crustacea in which distinct and functional gnathobasic processes are found on appendages far removed from the mouth.
The modifications which this original type undergoes are usually more or less plainly correlated with the functions which the appendages have to discharge.
Thus, when acting as swimming organs, the appendages, or their rami, are more or less flattened, or oar-like, and often have the margins fringed with long plumose hairs.
Very often one or other of the appendages may be modified for prehension, the seizing of prey or the holding of a mate.
This chelate condition may be assumed by almost any of the appendages, and sometimes it appears in different appendages in closely related forms, so that no very great phylogenetic importC ance can in most cases be attached to it.
The view is commonly held that these eye-stalks are really limbs, homologous with the other appendages.
The antennules (or first antennae) are almost universally regarded as true appendages, though they differ from all the other appendages in the fact that they are always innervated from the " brain " (or preoral ganglia), and that they are uniramous in the nauplius larva and in all the Entomostracan orders.
The antennae (second antennae) are of special interest on account of the clear evidence that, although preoral in position in all adult Crustacea, they were originally postoral appendages.
The maxillulae and maxillae (or, as they are often termed, first and second maxillae) are nearly always flattened leaf-like appendages, having gnathobasic lobes or endites borne by the segments of the protopodite.
In other Entomostraca considerable differentiation may take place, but the series is never divided into definite " tagmata " or groups of similarly modified appendages.
4) the abdominal appendages are constantly divided into an anterior group of three natatory " swimmerets " and a posterior group of three limbs used chiefly in jumping or in burrowing.
When present, the branchiae are generally differentiations of parts of the appendages, most often the epipodites, as in the Phyllopoda.
In the Isopoda the respiratory function has been taken over by the abdominal appendages, both rami or only the inner becoming thin or flattened.
Three series are distinguished, podobranchiae, attached to the proximal segments of the appendages, pleurobranchiae, springing from the body-wall, and an intermediate series, arthrobranchiae, inserted on the articular membrane of the joint between the limb and the body.
In some of the terrestrial Isopoda or woodlice (Oniscoidea) the abdominal appendages have ramified tubular invaginations of the integument, filled with air and resembling the tracheae of insects.
In the Mysidae among the Schizopoda a pair of similar otocysts are found in the endopodites of the last pair of appendages (uropods).
These may be formed by the modification of almost any of the appendages, often the antennules or antennae or some of the thoracic limbs, or even the mandibular palps (some Ostracoda).
In addition, some of the appendages in the neighbourhood of the genital apertures may be modified for the purpose of transferring the genital products to the female, as, for instance, the first and second abdominal limbs in the Decapoda.
The terminal part of the male ducts may be protrusible and act as an intromittent organ, or this function may be discharged by some of the appendages, as, for instance, in the Brachyura.
The rudiments of the first three pairs of appendages commonly appear simultaneously, and, even in forms with embryonic development, they show differences in their mode of appearance from the succeeding somites.
The appendages posterior to the mandibles appear as buds on the ventral surface of the somites, and in the most primitive cases they become differentiated, like the somites which bear them, in regular order from before backwards.
The limb-buds early become bilobed and grow out into typical biramous appendages which gradually assume the characters found in the adult.
The course of development here outlined, in which the nauplius gradually passes into the adult form by the successive addition of somites and appendages in regular order, agrees so well with the process observed in the development of the typical Annelida that we must regard it as being the most primitive method.
Further, the gradual appearance and differentiation of the successive somites and appendages may be accelerated, so that comparatively great advances take place at a single moult.
13, B), differing widely from the nauplius in form, and possessing all the appendages of the adult.
Another very common modification of the primitive method of development is found in the accelerated appearance of certain somites or appendages, disturbing the regular order of development.
Even in those which have most fully retained the primitive order of development, as in the Penaeidea and Euphausiidae, the last pair of abdominal appendages make their appearance in advance of those immediately in front of them.
14), the posterior five or six thoracic somites have their development greatly retarded, and are still represented by a short unsegmented region of the body at a time when the abdominal somites are fully formed and even carry appendages.
There is considerable reason for believing that the Ceratiocaridae, which are found from the Cambrian onwards, were allied to the existing Nebalia, and may possibly include the forerunners of the true Malacostraca, but nothing is definitely known of their appendages.
The large number and the uniformity of the trunk somites and their appendages, and the structure of the nervous system and of the heart in A pus, are Annelidan characters which can hardly be without significance.
It is probable also, as already mentioned, that the leaf-like appendages of the Phyllopoda are of a primitive type, and attempts have been made to refer their structure to that of the Annelid parapodium.
All the cephalic appendages are much reduced, the mandibles have no palps, and the maxillulae are vestigial.
In those Copepods in which the palps of the mandibles as well as the antennae are biramous and natatory, the first three pairs of appendages retain throughout life, with little modification, the shape and function which they have in the nauplius stage, and must, in all likelihood, be regarded as approximating to those of the primitive Crustacea.
It may be supposed to have approximated, in general form, to A pus, with an elongated body composed of numerous similar somites and terminating in a caudal furca; with the post-oral appendages all similar and all bearing gnathobasic processes; and with a carapace originating as a shell-fold from the maxillary somite.
The latter division, characterized by the possession of 19 somites and pairs of appendages (apart from the eyes), by the division of the appendages into two tagmata corresponding to cephalothorax and abdomen, and by the constancy in position of the generative apertures, differing in the two sexes, is unquestionably a natural group. The Entomostraca, however, are certainly a heterogeneous assemblage, defined only by negative characters, and the name is retained only for the sake of convenience, just as it is often useful to speak of a still more heterogeneous and unnatural assemblage of animals as Invertebrata.
The head is somewhat rudimentary and without eyes, but bears two dorsal appendages produced into numerous long filaments.
This group is characterized by the prolongation of the head into a rostrum or proboscis, at the end of which the mouth, with its appendages, is placed.
The mouth appendages are small; the mandibles, however, are stout.
It consists of a compact central mass and two straggling appendages running from its S.W.
In the deer of the sambar group, where the antlers never advance beyond a three-tined type, the shedding is frequently, if not invariably, very irregular; but in the majority at least of the species with complex antlers the replacement is annual, the new appendages attaining their full development immediately before the pairing-season.
Epidermal appendages are rare, the most frequent being marginal, saw-like, cartilaginous teeth, usually minute, but occasionally (Danthonia scabra, Panicum serratum) so large as to give the margin a serrate appearance.
The appendages of the second pair are large and prehensile, as in scorpions, but are armed with spines, to impale and hold prey.
The appendages of the third pair, representing the first pair of walking legs in spiders and scorpions, are, on the contrary, long, attenuated and manyjointed at the end.
namely the Amblypygi of which Phrynus is a commonly cited type, these tactile appendages are exceedingly long and lashlike, whereas in the tailed division, the Uropygi, of which Thelyphonus is best known, the limb is much shorter and less modified.
In the genus Cycas the female flower is peculiar among cycads in consisting of a terminal crown of separate leaf-like carpels several inches in length; the apical portion of each carpellary leaf may be broadly triangular in form, and deeply dissected on the margins into narrow woolly appendages like rudimentary pinnae.
In Ceratozamia the broad petiole-base is characterized by the presence of two lateral spinous processes, suggesting stipular appendages, comparable, on a reduced scale, with the large stipules of the Marattiaceae among Ferns.
Abies pectinata, &c.) the ripe cone differs from those of Pinus, Picea and Cedrus in the large size of the carpellary scales, which project as conspicuous thin appendages beyond the distal margins of the broader and more woody seminiferous scales; the long carpellary scale is a prominent feature also in the cone of the Douglas pine (Pseudotsuga Douglasii).
There are no teeth on the palate; pyloric appendages exist in great numbers; the vertebrae number fifty-three.
In the Graptoloidea certain lateral and vesicular appendages of the polypary in the Lasiograptidae have been looked upon as connected with the reproductive system; and in the umbrella-shaped synrhabdosomes already referred to, the common centre is surrounded by a ring of what have been regarded as ovarian capsules.
All round its head and also along the body the skin bears fringed appendages resembling short fronds of sea-weed, a structure which, combined with the extraordinary faculty of assimilating the colour of the body to its surroundings, assists this fish greatly in concealing itself in places which it selects on account of the abundance of prey.
- Pelmatozoa in which the theca is composed of an indefinite number of irregular plates, some of which are variously differentiated in different genera; with no subvective skeletal appendages, but with central mouth, from which there radiate through the theca five unbranched ambulacra, composed of a double series of alternating plates (covering-plates), sometimes supported by an outer series of larger alternating plates (sideplates or flooring-plates).
Ambulacral appendages take the form of: (I) circumoral tentacles, (2) sucking-feet, (3) papillae; of these (I) alone is always present.
Skeletal appendages are spines (radioles), pedicellariae, and, in some forms, minute sense-organs called sphaeridia.
Other epidermic appendages are the horns of ruminants and rhinoceroses - the former being elongated, tapering, hollow caps of hardened epidermis of fibrous structure, fitting on and growing from conical projections of the frontal bones and always arranged in pairs, while the latter are of similar structure, but without any internal bony support, and situated in the middle line.
The word, which means "jaw-footed," refers to the fact that in the members of the group, some of the lateral appendages or "feet" in the region of the mouth act as jaws.
The upright stems were attached to the soil by a number of dichotomously branched members (Stigmaria), which, whatever their morphological nature may be, appear to have performed the function of roots: they bore numerous cylindrical appendages, which penetrated the soil on all sides.
The names Condylopoda and Gnathopoda have been subsequently proposed for the same group. The word refers to the jointing of the chitinized exo-skeleton of the limbs or lateral appendages of the animals included, which are, roughly speaking, the Crustacea, Arachnida, Hexapoda (so-called " true insects "), Centipedes and Millipedes.
It is the existence in each ring of the body of a pair of hollow lateral appendages or parapodia, moved by intrinsic muscles and penetrated by bloodspaces, which is the leading fact indicating the affinities of these great sub-phyla, and uniting them as blood-relations.
(2) In all existing Arthropoda the region in front of the mouth is no longer formed by the primitive prostomium or head-lobe, but one or more segments, originally post-oral, with their appendages have passed in front of the mouth (prosthomeres).
At the same time the prostomium and its appendages cease to be recognizable as distinct elements of the head.
The brain no longer consists solely of the nerve-ganglion-mass proper to the prostomial lobe, as in Chaetopoda, but is a composite (syncerebrum) produced by the fusion of this and the nerve-ganglion-masses proper to the prosthomeres or segments which pass forwards, whilst their parapodia (= appendages) become converted into eye-stalks, and antennae, or more rarely grasping organs.
Lankester (2) was the first to suggest that (as is actually the fact in the Nauplius larva of the Crustacea) the prae-oral somites or prosthomeres and their appendages were ancestrally postoral, but have become prae-oral " by adaptational shifting of the oral aperture."
The appendages of the first prosthomere are not present as tentacles, as in Peripatus and Diplopods, but are possibly represented by the eyes or possibly altogether aborted.
The appendages of the second prosthomere are the well-known chelicerae of the Arach nids, rarely, if ever, antenniform, but modified as " retroverts" or clasp-knife fangs in spiders.
Diprosthomerous in the adult condition, though embryologically the appendages of somite II and the somite itself are, as here drawn, not actually in front of the mouth.
The three prosthomeres or prae-oral somites of Crustacea due to the sinking back of the mouth one somite farther than in Arachnida are not clearly indicated by coelomic cavities in the embryo, but their existence is clearly established by the development and position of the appendages and by the neuromeres.
The eyes in some Crustacea are mounted on articulated stalks, and from the fact that they can after injury be replaced by antennalike appendages it is inferred that they represent the parapodia of the most anterior prosthomere.
Sometimes the pair of appendages has not a merely tactile jointed ramus, but is converted into a claw or clasper.
The fourth somite is that in which the mouth now opens, and which accordingly has its appendages converted into hemignathous mandibles.
III, Coelom of the third prosthomere devoid of appendages.
7), but has no appendages.
Their appendages are respectively the mandibles and the gnathochilarium.
The five pairs of appendages of the post-oral somites of the head or prosoma thus constituted all primitively carry gnathobasic projections on their coxal joints, which act as hemignaths: in the more specialized forms the mandibular gnathobases cease to develop.
In Crustacea the fourth or mandibular somite never has less than the two following somites associated with it by the adaptation of their appendages as jaws, and the ankylosis of their terga with that of the prosthomeres.
But in higher Crustacea the cephalic " tagma " is extended, and more somites are added to the fusion, and their appendages adapted as jaws of a kind.
that the sessile eyes of other B, An oral papilla, one of Crustacea, and of other Arthropoda the second pair of post-oral generally, indicate the position of appendages.
appendages which have atrophied.'
C, One of the first post-oral From what has been said, it is pair of appendages or manapparent that we cannot, in attemptdibles; cl', el', the greatly ing to discover the affinities and enlarged claws.
(Compare A.) divergences of the various forms of The appendages are repreArthropoda, attach a very high sented with the neural or phylogenetic value to the coincidence ventral surface uppermost.
Milne-Edwards, who was followed by Huxley, long ago formulated the conclusion that the eye-stalks of Crustacea are modified appendages, basing his argument on a specimen of Palinurus (figured in Bateson's book (1), in which the eye-stalk of one side is replaced by an antenniform palp. Hofer (6) in 1894 described a similar case in Astacus.
The rami may be flattened for swimming, when it is " a bi-ramose swimmeret," or both or only one may be filiform and finely annulate; this is the form often presented by the antennae of Crustacea, and rarely by prae-oral appendages in other Arthropods.
(7) The endopoditic ramus is greatly enlarged and flattened, without or with only one jointing, the corm (basal segment) is evanescent; often the plate-like endopodites of a pair of such appendages unite in the middle line with one another or by the intermediary of a sternal up-growth and form a single broad plate.
It may be pointed out that the most radical difference presented in this list is that between appendages consisting of the corm alone without rami (Onychophora) and those with more or less developed rami (the rest of the Arthropoda).
(a) The integument is covered by a delicate soft cuticle (not firm or plated) which allows the body and its appendages great range of extension and contraction.
(b) The paired claws on the ends of the parapodia and the fanglike modifications of these on the first post-oral appendages (mandibles) are the only hard chitinous portions of the integument.
(c) The head is deuterognathous - that is to say, there is only one prosthomere, and accordingly the first and only pair of hemignaths is developed by adaptation of the appendages of the second somite.
(d) The appendages of the third somite (second post-oral) are clawless oral papillae.
(e) The rest of the somites carry equi-formal simple appendages, consisting of a corm or axis tipped with two chitinous claws and devoid of rami.
The separation of the heavier plates of chitin by grooves of delicate cuticle results in the hinging or jointing of the body and its appendages, and the consequent flexing and extending of the jointed pieces.
(d) Rarely only one, and usually at least two, of the somites following the mandibular somite carry appendages modified as jaws (with exceptions of a secondary origin).
(e) The rest of the somites may all carry appendages, or only a limited number may carry appendages.
In all cases the appendages primarily develop rami or branches which form the limbs, the primitive axis or corm being reduced and of insignificant size.
In the most primitive stock all the post-oral appendages had gnathobasic outgrowths.
Only one somite following the first post-oral or mandibular segment has its appendages modified as jaws.
The somites of the body, except in Pauropus, either fuse after early development and form double somites with two pairs of appendages (Julus, &c.), or present legless and leg-bearing somites alternating.
Head tritognathous and diprosthomerous - that is to say, with two prosthomeres, the first bearing typical eyes, the second a pair of appendages reduced to a single ramus, which is in more primitive forms antenniform, in higher forms chelate or retrovert.
As many as six pairs of appendages following the mouth may have an enlarged gnathobase actually functional as a jaw or hemignath, but a ramus is well developed on each of these appendages either as a simple walking leg, a palp or a chela.
Their position is:unknown in the more primitive forms. The more primitive forms have branchial respiratory processes developed on a ramus of each of the post-oral appendages.
Head tetartognathous and triprosthomerous - that is to say, with three prosthomeres; the first bearing typical eyes, the second a pair of antenniform appendages (often bi-ramose), the third a pair of appendages usually antenniform, sometimes claw-like.
Besides the first post-oral or mandibular pair, at least two succeeding pairs of appendages are modified as jaws.
The appendages of four or more additional following somites may be turned upwards towards the mouth and assist in the taking of food.
A characteristic, comparable in value to that presented by the pygidial shield of Arachnida, is the frequent development of a pair of long appendages by the penultimate somite, which with the telson form a trifid, or, when that is small, a bifid termination to the body.
The two somites following the mandibular or first post-oral or buccal somite carry appendages modified as maxillae.
The fourth post-oral somite has its appendages converted into very large and powerful hemignaths, which are provided with poison-glands.
The first prosthomere has its appendages represented by the compound eyes and a protocerebrum, the second has the antennae for its appendages and a deutocerebral neuromere, the third has suffered suppression of its appendages (which corresponded to the second pair of antennae of Crustacea), but has a tritocerebrum and coelomic chamber.
The somites following the head are strictly nomomeristic and nomotagmic. The first three form the thorax, thhe appendages of which are the walking legs, tipped with paired claws or ungues (compare the homoplastic claws of Scorpio and Peripatus).
It appears from observation of the embryo that whilst the first prosthomere of Centipedes has its appendages reduced and represented only by eye-patches (as in Arachnida, Crustacea and Hexapoda), the second has a rudimentary antenna, which disappears, whilst the third carries the permanent antennae, which accordingly correspond to the second antennae of Crustacea, and are absent in Hexapoda.
The somites of the abdomen all may carry rudimentary appendages in the embryo, and some of the hinder somites may retain their appendages in a modified form in adult life.
The appendages of the eighth and tenth abdominal somites are modified as gonapophyses.
The Hexapoda are not only all confined to a very definite disposition of the somites, appendages and apertures, as thus indicated, but in other characters also they present the specialization of a narrowly-limited highly-developed order of such a class as the Crustacea rather than a range from lower more generalized to higher more specialized forms such as that group and also the Arachnida present.
On the other hand, the facts that the Hexapoda and the Chilopoda have triprosthomerous heads, that the Hexapoda have the same total number of somites as the nomomeristic Crustacea, and the same number of opisthomeres in the head as the more terrestrial Crustacea, together with the same adaptation of the form of important appendages in corresponding somites, and that the compound eyes of both Crustacea and Hexapoda are extremely specialized and elaborate in structure and identical in that structure, all lead to the suggestion that the Hexapoda, and with them, at no distant point, the Chilopoda, have branched off from the Crustacean main stem as specialized terrestrial lines of descent.
A gnathobase is developed (in the primitive stock) on every pair of post-oral appendages; two prosthomeres present, the second somite as well as the first having passed in front of the mouth, but only the second has appendages.