ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
163 
extends into tbe cavity of the pouch, which at this stage is being con- 
stricted from the free end of the archenteron. Twelve hours later the 
blastopore has closed, the posterior end of the archenteron lies loose in 
the larva except for its support from the mesenchyme, the anterior end 
bends over and fuses with an invagination which forms the mouth and 
oesophagus. Encircling the oesophagus lies the already five-rayed but 
horse-shoe-shaped hvdrocoel. Lying on the top of the stomach and 
still connected with it, is the pouch which will form finally the hypo- 
gastric enterocoel of Goto. 
On the left side, at the point where hydrocoel and enterocoel are in 
open communication, the pore-canal arises and passes dorsalwards. 
Dorsal to the stomach lies the pouch, which will ultimately form the 
epigastric enterocoel of Goto. 
In a sixty-hour larva, the cilia are restricted to four transverse bands. 
The anterior end of the larva, which will enter directly into the forma- 
tion of the star, is very much widened, and gives to the whole a club- 
shape. Encircling the mouth are five groups of rounded ectodermic 
elevations, due to the pushing out of the terminal tentacles and first 
pair of foot-tentacles. From the very first appearance of any part of 
the adult structure, it has a direct and constant relation to the larval 
body. In fact, in the life-history of 0. olivacea, there is a complete veri- 
fication of the conclusion arrived at by Goto in his study of the relation 
of the adult form to the larva in Asterias pallida. 
Development of Ophiocoma echinata.* — Mr. C. Grave gives a short 
account of this. The orange-red eggs formed a prickly egg membrane 
after fertilisation. Regular segmentation resulted in a blastula with a 
very small cavity, which burst the cliitinous membrane, and swam about, 
revolving on its long axis. At the time of hatching the mesenchyme 
formation began in a rapid proliferation of cells at the “vegetative 
pole,” or “ vegetable pole,” as the author calls it. The gastrula is 
formed several hours later by the invagination of the same pole. From 
the apex of the flattened archenteron a pair of pouches are constricted 
off to right and left. Each divides into two, one of which remains in 
about its original position, while the other migrates towards the blasto- 
pore, and takes up a position on the side of that part of the archenteron 
which will later become the stomach. The right posterior pouch de- 
generates and disappears. Soon after their formation, the two anterior 
pouches both communicate with the exterior, through pore canals that 
open on the dorsal surface of the larva, which are not intra-cellular 
structures, but are lined with epithelium. At about the time of the 
formation of the pore-canals or a little before, the larval mouth breaks 
through on the ventral surface, and there is formed the perfectly bi- 
laterally symmetrical larva. The right pore-canal sooner or later dis- 
appears, but persists slightly longer than the right posterior pouch, 
which is very transitory. 
Species of Echmocardium.f — R. Koehler discusses the species of 
Echinocardium found in the Mediterranean, and gives more adequate 
diagnoses than heretofore of Ech. cor datum, Ech. flavescens, and Ech. 
* Johns Hopkins TJniv. Circ., xviii. (1898) pp. 6-7 (6 figs.). 
t Rev. Suisse Zool., vi. (1899) pp. 173-87 (1 ph). 
