412 
ORIGINAL ARTICLES. 
ring, with a coecal process passing to the surface on the dorsal aspect. 
The central dark mass indicates the position of the stomach of the 
starfish, the circular vessel of the ambulacral ring, and the vascular 
coecum of the sand canal. 
The nascent organs of the starfish were entirely unconnected with 
the alimentary system of the pseudembryo. 
In an individual slightly farther advanced the body had become 
pentagonal (Fig. 4, B.), the ambulacral ring, and the included gra¬ 
nular mass were more marked. The provisional mouth was still 
distinct near one of the salient angles, and the .intestine could be 
traced curving round the outside of the vascular ring, and ending by 
an anal pore on the dorsal surface of the rays. 
The internal organs of the starfish now progressed steadily in de¬ 
velopment, inclosed in the structureless granular substance of the 
pseudembryo, whose alimentary canal still remained well defined and 
entire. Five blunt rays gradually became studded with spines and 
paxillse, and weretermined by red eye-spots. The permanent mouth 
of the starfish was defined in the centre of the ventral surface, though 
still closed by a membrane, and at length the ambulacral vessels 
might be detected. 
The granular sarcode-substance characteristic of the pseudembryo 
now seemed to thin off the surface. The provisional alimentary 
canal gradually disappeared, though it was only after the extrusion 
of the embryo from the marsupium , that the permanent mouth of 
the starfish came into play by the absorption of the occluding mem¬ 
brane. 
36. I have much hesitation in associating with that of Pteraster 
militarise the pseudembryo of Asteracanthion glacialis (L.), briefly 
described by Dr. Busch. # The author only had it in his power to 
observe this form during a single day, and his fragmentary observa¬ 
tions left it in doubt whether the pseudembryo was progressing 
towards the “ Bipinnaria” type, or towards some simple form of 
development. The figures of the pseudembryo resemble somewhat 
those of the early stages of Pteraster militaris. I briefly abstract Dr. 
Busch’s description, in anticipation of further information. When 
the process of segmentation is complete, an oval germ escapes from 
the vitelline envelope. A day after extrusion, a dusky 
rounded mass may be observed in the centre, the first 
indication of the stomach. A broad yellowish border 
now becomes defined, passing right round the body, and, 
at the same time, the digestive cavity elongates and 
stretches to the free border, where it ends in a large 
round mouth. The body now becomes lengthened, and 
clear cells appear at intervals over the surface, f 
* Op. cit. 
f Fig. 5. Asteracanthion glacialis (L.) Pseudembryo. a. Pseudembryonic 
assimilative cavity. (After Busch.) 
