25, C) to the inner face of the vesicle, thus forming the mesoblast.
8); the primitively open cup has now closed over to form a vesicle lying beneath the ectoderm; the outer wall of the vesicle becomes thickened to form a cellular lens (1), while the proximal wall consists of sensory and pigmented cells and forms a retina.
M, The water - pore, leading by the stone - canal stc to the waterring, from which hangs a Polian vesicle pb.
Bergh (for Lumbricus and Criodrilus), whose figures show a derivation of the entire nephridium from mesoblast, and an absence of any connexion between successive nephridia by any continuous band, epiblastic or mesoblastic. A midway position is taken up by Wilson, who asserts the mesoblastic formation of the funnel, but also asserts the presence of a continuous band of epiblast from which certainly the terminal vesicle of the nephridium, and doubtfully the glandular part of the tube is derived.
It contains a closed vesicle regarded by Schepotieff as a right probosciscavity and in any case representing the pericardium of Balangolossus, the glomerulus of which is also probably represented.
RHIPIDOGL0ssA.-Aspidobranchia with a palliovisceral anastomosis (dialyneurous); eye-vesicle closed, with crystalline lens; ctenidia, osphradia and hypobranchial glands paired or single.
In accordance with this view there would be also some probability in favour of regarding the collar nerve-tube of the Enteropneusta as the equivalent of the cerebral vesicle only of Amphioxus and the Ascidian tadpole, and also of the primary forebrain of vertebrates.
7, ect), which later invaginates to form the inner vesicle of the polypide-bud.
The escape of the insect takes place on the spontaneous bursting of the walls of the vesicle, probably when, after viviparous (thelytokous) reproduction for several generations, male winged insects are developed.
- a, Atrium; al, alimentary canal; y blood-vessel; cv, cerebral vesicle; df, dorsal section of myocoel (= fin spaces); e, " eyespot"; end, endostyle; gl, club-shaped gland; lm, edge of left metapleur; m, lower edge of mouth; n, notochord; nt, pigmented nerve tube; ps, primary gill-slits, I, 9, and 14; rc, renal cells on atrial floor; rm, edge of right metapleur; so, sense organ opening into praeoral pit; ss, thickenings, the rudiments of the row of secondary gill-slits.
In 1835 he communicated to the Munich academy of sciences his researches on the physiology of generation and development, including the famous discovery of the germinal vesicle of the human ovum.
We then find the typical otocyst of the Leptomedusae, a vesicle bulging on the ex-umbral side of the velum (figs.
To enclose the club in a protective covering form- ?0 ing a cup or vesicle, at first open distally; finally the opening closes and J' P g, ,.
Next the pit closes up to form a vesicle with a pore, and so gives rise to the pneumatophore.
In birds, this stalk consists entirely of blood-vessels, which in the adult enclose no terminal vesicle, and fuse with the membranous linings of the skull.
The eye is always a closed vesicle, and the internal cornea is extensive.
Y, Vesicle on genital duct.
By the pulsation of the pericardial vesicle (best observed in the larva) the blood is driven into the glomerulus, from which it issues by efferent vessels which effect a junction with the ventral (sub-intestinal) vessel in the trunk.
The outer single layer of cells which constitutes the surface of the vesicle is the ectoderm or epiblast.
Posterior superior iliac spine Ureter Great sciatic notch Vas deferens; Spine of ischium Vas deferens Seminal vesicle Bladder wall Levator ani Prostate 9, ?
In Fucus vesiculosus they arise in lateral pairs; in Ascophyllum they are single and median; in Macrocystis one vesicle arises at the base of each thallus segment; in Sargassum and Halidrys the vesicles arise on special branches.
Over the cerebral eye there is a small orifice placed to the left of the base of the cephalic fin, leading into a pit which extends from the surface of the body to the surface of the cerebral vesicle; this is known as A.
The nephridia of the first three pairs of legs are smaller than the rest, consisting only of a vesicle and duct.
Knob, in which the oto liths are exposed, the second that of a closed vesicle, in which the oto liths are covered over.
A considerable portion of the rectum and the upper part of the right seminal vesicle have been taken away.
Posterior superior iliac spine Cut end of rectum Apex of sacrum Great sciatic notch Ureter Peritoneum Spine of ischium Bladder wall Seminal vesicle Tuberosity of ischium Ischio-rectal fossa Cut end of rectum External sphincter ani Gluteus maximus better seen in young the prostate the urethra runs more forward for about threequarters of an inch, lying between the two layers of the triangular From C. S.
S, Vesicle of segmental organ.
The internal vesicle is already indicated, and is shown in the diagram by the thinner black line: I, gut; 2, somite; 2', nephridial part of coelom; 3, haemocoele; 3', part of haemocoele which will form the heart - the part of the haemocoele on each side of this will form the pericardium; 4, nerve-cord; 4, slime glands.
The coelom is represented as surrounded by a thick black line, except in the part which forms the internal vesicle of the nephridium.
The process carrying the otolith outer side of a or concretion hk, formed by endoderm cells, is tentacle, two enclosed by an upgrowth forming the " vesicle," nerves run round which is not yet quite closed in at the top. the base of the (After Hertwig.) tentacle to it.
Becomes a vesicle, the future r.c, Radial canal.
The essential difference between these two kinds of eye appears to be that the Chaetopod eye (in its higher developments) is a vesicle enclosing the lens, whereas the Arthropod eye is a pit or series of pits into which the heavy chitinous cuticle dips and enlarges knobwise as a lens.
S.o.t, Third portion of nephridium broken off at p.f from the internal vesicle, which is not shown.