626 
ZOOLOGICAL LITERATURE. 
deuterozooid, which appear sooner than in Bipinnaria, and assume a greater 
relative magnitude. The ambulacral system has two distinct rudiments, and 
its five cjeca remain distant from each other till a comparatively late period* 
The homologue of the ciliated sac is in connexion with three characteristic 
prehensile appendages (Brachiolaria). 
B. The ovum is developed within a marsupium,” and gives rise to a 
protozooid destitute of special swimming-appendages. The deuterozooid does 
not appear as a distinct hud, and its structures at an early period predominate 
over those of the protozooid, which soon wither away or are absorbed. 
1. The marsupium is extemporized by the infolding of the rays over the 
oral region of the adult starfish. The protozooid has no alimentary canal, 
but is furnished with prehensile appendages corresponding to those of Bra- 
chiolaria (young of Echinaster sanguinolentus, Asteracanthion miilleri, A. vio- 
laceum, and an American species observed by Desor and Agassiz). 
2. The marsupium consists of a distinct membranous fold, supported by 
the spines over the dorsal surface of the adult. The protozooid possesses an 
alimentary canal, no part of which would seem to be appropriated by the 
deuterozooid (young of Pteraster militaris, perhaps also of Ast&i'acanthion 
glaciale). 
The position of the anus next to the mouth is an eminently 
crinoidal feature of the young A. pallidum, as is likewise the 
arrangement of its dorsal plates ; while its arched disk and tall 
spines ‘^remind us of the Echinoids.^^ A. Agassiz notes also 
the constant appearance of the madreporic rudiment in the same 
situation, and consequently the definite relations of the madre- 
poric body to the axes of the adult starfish. The position of 
this structure on the oral surface of the embryonic disk is a 
feature of the Ophiurans.^^ Here our author might have referred 
to the marginal position of the madreporic body in Asbjornsen^s 
singular genus Bi'is sing a, y/liich unites the characters of three 
orders of starfishes — in its ambulacral grooves, spinous arms 
affixed to a distinct central disk, and reproductive organs brachial 
in position like those of Comatula, 
With regard to grade of development, A. Agassiz concludes, 
on embryological grounds, that Asterids with suckers rank 
above those with tentaculiform feet j those with four rows of 
suckers, above those with only two ; those with complicated 
spines and plates, above those with smooth arms ; and, lastly, 
those with elongated arms, above starfishes whose outline is 
pentagonal. 
The seven species of Asterids found by Grube (pp. 105 & 106) 
at Lossini are well-known Mediterranean forms. 
