2, nch.), growing forwards in the septum between the proboscis-cavity and the collar-cavities, and supported dorsally by the median mesentery of the collar, is the representative of the so-called notochord or stomochord of Balanoglossus; and if the view that this organ is really a notochord is well founded, it may be regarded as the homologue of the anterior end of the Vertebrate notochord.
As additional features of the subclass may be mentioned the absence of a corpus callosum connecting the right and left hemispheres of the brain,' and of a fossa in the septum between the two auricles of the heart.
At the age of puberty the lad was tattooed or scarred with gashes cut in back, shoulders, arms and chest, and the septum of the nose was pierced.
The arches bear on the convex outer side the delicate arborescent gills, and on the concave inner side develop a membranous septum with vermicular perforations, a special sifting or filtering contrivance through which the water absorbed by the mouth has to pass before reaching the respiratory organs of the branchial apparatus.
The orbito-sphenoids diverge only posteriorly, otherwise they are practically unpaired and form the median interorbital septum, which is very large in correlation with the extraordinary size of the eyeballs.
The nasal septum is often more or less incomplete, producing nares perviae, e.g.
The interauricular septum is mostly entirely membranous; in the middle it is thinner, rather transparent, but there is no depression or fossa ovalis.
One set lies in front of the diaphragm, which is the most anterior and complete septum, the rest having disappeared or being much less developed.
The gonads are, moreover, limited and fixed in numbers, and are practically invariably attached to the intersegmental septa, usually to the front septum of a segment, more rarely to the posterior septum.
Fibrous septum, behind the periLiver.
To the left of the ctenidium a pulmonary sac, separated from it by an incomplete septum, am phibious.
The vomer is broad, abruptly truncated in front, and deeply cleft behind, so as to embrace the rostrum of the sphenoid; the palatals have produced postero-external angles; the maxillo-palatals are slender at their origin, and extend obliquely inwards and forwards over the palatals, ending beneath the vomer in expanded extremities, not united either with one another or with the vomer, nor does the latter unite with the nasal septum, though that is frequently ossified.
Like the body, the proboscis is hollow, and its cavity is separated from the body cavity by a septum or proboscis sheath.
Traversing the cavity of the proboscis are muscle-strands inserted into the tip of the proboscis at one end and into the septum at the other.
Vs, ventral septum of proboscis.
The pistil, which is above the rest of the members of the flower, consists of two carpels joined at their edges to form the ovary, which becomes two-celled by subsequent ingrowth of a septum from these united edges; a row of ovules springs from each edge.
D, Lunaria biennis, showing the septum B, Lepidium sativum.
In Magellania [Waldheimia] it is elongated and reflected; the hinge-plate large, with four depressions, under which originates a median septum, which extends more or less into the interior of the shell (figs.
In Bouchardia the septum only is furnished with two short anchor-shaped lamellae.
A, ventral, B, dorsal valves; 1, loop; q, crura; ss, septum; c, cardinal process.
The liver cells, therefore, are entodermal, but the supporting connective tissue mesodermal from the septum transversum.
At first the liver is embedded in the septum transversum, but later the diaphragm and it are constricted off one from the other, and soon the liver becomes very large and fills the greater part of the abdomen.
In the filaments of the gill of Protobranchia and many Filibranchia the tubular cavity is divided by a more or less complete fibrous septum into two channels, for an afferent and efferent blood-current.
Septibranchia Gills have lost their respiratory function, and are transformed into a muscular septum on each side between mantle and foot.
- Siphons short and separate; branchial siphon with a large valve; branchial septum bears two groups of orifices on either side; hermaphrodite.
- Branchial septum with three groups of orifices on each side; siphons short, separate, branchial siphon with a valve.
- Branchial septum with four or five pairs of very narrow symmetrical orifices; siphons long, united, their extremities surrounded by tentacles; sexes separate.
Between the two corpora cavernosa the sheath is not complete and, having a comb-like appearance, is known as the septum pectinatum.
The spores themselves may be unicellular without a septum or multicellular with one or more septa.
A simple sporophore may be merely a single short hypha, the end of which stops growing and becomes cut off as a conidium by the formation of a septum, which then splits and allows the conidium to fall.
More generally the hypha below the septum grows forwards again, and repeats this process several times before the terminal conidium falls, and so a chain of conidia results, the oldest of which terminates the series (Erysiphe); when the primary branch has thus formed a basipetal series, branches may arise from below and again repeat this process, thus forming a tuft (Penicillium).
A second type is developed as follows: the primary hypha forms a septum below its apex as before, and the terminal conidium, thus abstricted, puts out a branch at its apex, which starts as a mere point and rapidly swells to a second conidium; this repeats the process, and so on, so that we now have a chain of conidia developed in acropetal succession, the oldest being below, and, as in Penicillium, &c., branches put forth lower down may repeat the process (Hormodendron).
Without a bony nasal septum between the nostrils..
Together with man and the baboons, the anthropoid apes form the group known to science as Catarhini, those, that is, possessing a narrow nasal septum, and are thus easily distinguishable from the flat-nosed monkeys or Platyrhini.
Across the long axis, by the formation of a septum, which either splits at once or remains intact for a shorter or longer time.
The growth of an ordinary bacterium consists in uniform elongation of the rodlet until its length is doubled, followed by division by a median septum, then by the simul- Measure- taneous doubling in length of each daughter cell, again ment of followed by the median division, and soon (figs.
In Central and South America alligators are represented by five species of the genus Caiman, which differs from Alligator by the absence of a bony septum between the nostrils, and the ventral armour is composed of overlapping bony scutes, each of which is formed of two parts united by a suture.
This steel septum was protected on either side by a thin wall of asphaltic concrete supported by rubble stone embankments, and owing to irregular settling of 'the embankments became greatly distorted, apparently, however, without causing leakage.
In addition to these parts the following structures may exist in corals:- Dissepiments are oblique calcareous partitions, stretching from septum to septum, and closing the interseptal chambers below.
Ec, Ectoderm; en, endoderm; mg, mesogloea; m, m, mesenteries; s, septum; b, basal plate formed of ellipsoids of carbonate of lime secreted by the basal ectoderm; ep, epitheca.
16 and 17 that every ec septum is covered by a fold of endoderm, mesogloea, and ectoderm, and is in fact pushed into the cavity of the zooid from without.
In this coral the calicle is divided into quadrants by four principal septa, the main septum, counter septum, and two alar septa.
The remaining septa are so disposed that in the quadrants abutting on the chief septum they converge towards that septum, whilst in the other quadrants they converge towards the alar septa.
The secondary septa show a regular gradation in size, and, assuming that the smallest were the most recently formed, it will be noticed that in the chief quadrants the youngest septa lie nearest to the main septum; in the other quadrants the youngest septa lie nearest to the alar septa.
Again, in the family Amphiastraeidae there is commonly a single septum much larger than the rest, and it has been shown that in the young calicles, e.g.
The trabeculae are united together by these thickened internodes, and the result is a fenestrated septum, which in older septa may become solid and aporose by continual deposit of calcite in the fenestrae.
Further, the trabeculae may be evenly spaced throughout the septum, or may be grouped together, and this feature is probably of value in estimating the affinities of corals.
M, Main septum; c, counter septum; t, t, alar septa.
(In this Devonian genus there is a single semicircular operculum furnished with a stout median septum and numerous feebly developed secondary septa.
A, Longitudinal section of the rhizome, including a node and portions of the adjoining internodes; k, septum between the two internodal cavities, hh; gg, vascular bundles; 1, vallecular canal; s, leaf-sheath.