ANATOMY, PHYSIOLOGY, ETC. 
BcL 6 
cavity of segnientatiou. The gastro -vascular cavity of the Ccelenterata, 
therefore, is homologous only with the primitive intestinal cavity of 
Echinoderms, of which the later body-cavity and the water- vascular 
system, &c., are only evaginations. The calcareous corpuscles of the skin 
are formed in the ectoderm. 
The investigations of Gotte (8) have cleared up some highly import- 
ant and hitherto obscure points in the developmental history of Crinoidea 
{Antedon)y thus making it possible to institute a closer comparison be- 
tween the structure of the larvae of this and of the other sub -classes of 
Echinoderms. Apart from much that is different, there are some 
striking analogies with the facts just settled for the Holothuriidce by 
Selenka. The primitive intestine is introduced in the “gastrula” 
through an invagination of the blastoderm, but the intestinal cavity thus 
formed is very soon completely closed up. Through evagination from 
it, three secondary cavities are formed, two (lateral) forming the left 
(inferior, or actinal) and the right (superior, or abactinal) peritoneal 
cavity, the third (^ventral) giving origin to the aquiferous system and 
the tentacula. It is only after the first elements of the stem, its calcareous 
articles and terminal plate, are deposited in the posterior portion of the 
larval body, and after the appearance of the centro-dorsal plate, the 
basalia, and oralia in the anterior portion, that the whole visceral portion 
so far changes its position in the body as eventually to fill up the portion 
diametrically opposed to the base of the stem ; then also the coverlet 
over the tentacles breaks down, and the mouth and vent are formed, the 
last-named orifice at a place nearly answering to the former position of 
the gastrular invagination. According to Carpenter (4), who describes 
and figures some later stages of the development of the young (penta- 
crinoid) Antedon, and illustrates their anatomy, the vent is, however, 
formed at a somewhat later stage. The second portion of Gotte’s paper 
is devoted to a sagacious and profound analysis of the homologies of the 
larvsB of the five sub-classes of Echinoderms, which it is impossible here 
to reproduce ; still it may be noted that the oral (actinal) portion of 
the body of a starfish, brittle-star, or sea-urchin, with the arms in 
the stars, is formed from and corresponds to the left antimere of the 
larva, the dorsal (abactinal) to the right ; that the Crinoids may be con- 
sidered as the most primitive type among the Echinodermata ; that the 
primitive coverlet over the pre-oral cavity gives a clue towards under- 
standing the apparently mouthless palaeozoic Crinoids, — abnormal stem- 
less forms of larval Antedon in like manner suggesting Holopus ; that 
the centro-dorsal portion of the starfish, or brittle-star, corresponds with 
the whole dorsal (abactinal) portion of the sea-urchin, and not, inversely, 
the apex of the Echini to the whole dorsal portion of disc and arms in 
Asterioe and Ophiurce ; that the “ radii ” of Holothurians are truly the 
“ interradii ” ; and that the structural disharmony between the larvae of 
Echinoderms and of worms (including those of Gephyrea), excludes the 
possibility of any theory connecting these types genealogically being 
conformable with truth. Greeff (7) also illustrates the structure of an 
embryonal Antedon before the protrusion of the first tentacles. 
The observations of Hertwig (9) on the processes going on in the egg 
