PTEROBRANCHIA, a zoological group established by Ray Lankester in 1877.
Ray Lankester) that this condition has been arrived at through some such intermediate stage as that offered by Polychaet Magelona.
Ray Lankester to the members of a series of tubes, proved in some cases to be excretory in nature, which exist typically to the number of a single pair in most of the segments of the Chaetopod body, and open each by a ciliated orifice into the coelom on the one hand, and by a pore on to the exterior of the body on the other.
Goodrich, endorsed by Lankester, led to the opinion that under the general morphological conception of "nephridium" were included two distinct sets of organs, viz.
There are, however, anatomical and histological differences to be seen at any rate at the extremes between the undoubted nephridia of Goodrich, Meyer and Lankester, and the coelomoducts of the same authors.
In this category are included (by Goodrich and Lankester) the gonad ducts of the Oligochaeta, certain funnels without any aperture to the exterior that have been detected in Nereis, &c., funnels with wide and short ducts attached to nephridia in other Polychaeta, gonad ducts in the Capitellidae, the gonad ducts of the leeches.
Lankester, Introductory Chapter in A Treatise on Zoology; E.
Lankester in the ninth edition of this work attributed it to the pressure of the shell and visceral hump towards the right side.
(Lankester.) x, y, The median antero-posterior axis.
(Lankester.) c, Muscular bundles forming the root of the foot, and adherent to the shell.
(Lankester.) the animal into the large anterior region of the sub-pallial space.
On cutting away the anterior part of the mantle-skirt so as to expose the sub-pallial chamber in the region of the neck, we find the right and left renal papillae (discovered by Lankester in 1867) on either side of the anal papilla (fig.
6, d), which were originally described by Lankester as orifices possibly connected with the evacuation of the generative products.
Demonstrated by Lankester in 1867, at a pie, Pedal nerve.
The capito-pedal organs of Lankester (= rudimentary ctenidia).
(Lankester.) f, Papilla of the larger nephridium.
(Lankester.) q, Intestine in transverse section.
(Lankester.) o, Mouth.
(Lankester.) a, Cephalic tentacle.
(Lankester.) A, Simple introvert completely introverted.
(After Lankester, 17.) dc, Directive corpuscle (outcast cell).
Lankester as a branch of the Cephalopoda, chiefly on account of the protrusible suckerbearing processes at the anterior end of Pneumonoderma.
(All from Lankester.) by the mantle-skirt, is the ctenidium with its free end turned backwards.
(Lankester.) Anterior cephalic tentacle.
60), at one time supposed to be the developing anus, but shown by Lankester to be identical with the " shell-gland " discovered by him in other Mollusca (Pisidium, Pleurobranchidium, Neritina, &c.).
Lankester, whilst H.
(Lankester.) ph, Pharynx (stomodaeal inattachment to the ecto vagination).
The other extreme end closes, but the invaginated endoderm cells remain in continuity with this extremity of the blastopore, and form the " rectal peduncle " or " pedicle of invagination " of Lankester, although the endoderm cells retain no contact with the middle region of the now closed-up blastopore.
Ray Lankester, pt.
Ray Lankester, " Mollusca," in 9th ed.
Lankester the arrangement is " nomomeristic " and " nomotagmic."
(From Lankester, Q.
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.
Once the identity of the chilaria with the pentagonal sternal plate of the scorpion is recognized - an identification first insisted on by Lankester - the whole series of segments and appendages in the two animals, Limulus and Scorpio, are seen to correspond most closely, segment for segment, with one another (see figs.
Has been shown by Lankester Letters as in fig.
Differ; but the lateral eyes of Scorpio were shown by them (After Lankester, loc. cit.) to be similar in structure to the lateral eyes of Limulus, and the central eyes of Scorpio to be identical in structure with the central eyes of Limulus (see below).
That this (Alter Lankester, loc. cit.) in-sinking has taken place, and that the lung-books or in-sunken gill-books of Scorpio really represent appendages (that is to say, limbs or parapodia) is proved by their developmental history (see FIG.
(After Lankester, toe cit.) Magnified MOO p GC. D R.
(From Lankester, loc. cit.) figs.
VII, Usually considered to be the tergum of the genital somite, but suggested by Pocock to be that of the other [According to the system of numbering explained in the text, if VII is the tergum of the praegenital somite (as is probable) it should be labelled Prg without any number, and the somites VIII to XIII should be lettered 1 to 6, indicating that they are the six normal somites of the mesosoma; whilst XV to XVIII should be replaced by the numbers 7 to 12 - an additional suppressed segment (making up the typical six) being reckoned to the metasomatic fusion.] (From Lankester, Q.
Correspond exactly in structure, the narrow, flat blood-space in the lamellae being interrupted by pillar-like junctions of the two surfaces in both cases (see Lankester (4)), and C ?8222;?
42) the six somites of the mesosoma are not fused to form a carapace at an early stage, and they are followed by three separately marked metasomatic somites; the other three somites of the metasoma have disappeared in Limulus, but are represented (From Lankester, loc. cit.) by the unsegmented prae-anal region.
(After Lankester, loc. cit.) the last pair of legs in both Scorpio and Limulus, viz.
(From Lankester, loc. cit.) palpiform appendages.
The struc ture of the lateral eye of Limulus was first described by Grenacher, and further and more accurately by Lankester and Bourne (5) and by Watase; that of Scorpio by Lan kester and Bourne, FIG.
(For details the reader is referred to Watase (11) and to Lankester and Bourne (5).) The structure of the central eyes of Scorpio and spiders and also of Limulus differs essentially from that of the lateral eyes in having two layers of cells (hence called diplostichous) beneath the lens, separated from one another by a membrane (figs.
(From Lankester, loc. cit.) forming a star-like chitinous centre in section, each lateral eye of Scorpio has several rhabdoms of five or less rhabdomeres, indicating that the Limulus lateral eye-unit is more specialized than the detached lateral eyelet of Scorpio, so as to present a coincidence of one lens with one rhabdom.