128 BULLETIN OF THE 
that the gastral mouth serves for reception of food until the formation 
of the real mouth (second opening). Salenka* says of the view of 
Krohn: ‘Ich kann dieser Ansicht nicht beitreten die nach aussen 
schlagenden Geisselendes Urdarms scheinen den Eintritt von fremden 
Stoffen durchaus zu verhindern.” 
A. Agassiz says that in the starfish and Strongylocentrotus gastrula 
currents of water enter the mouth, pass into the stomach, and pass out 
through the same opening. The gastrula mouth in these instances cer- 
tainly serves as both mouth and anus. 
Food was not seen to enter the mouth of the gastrula of Echinarach- 
nius, and no observations were made on currents of water. The open- 
ing of the blastopore has probably the same function as the homologous 
opening in Asterias and Strongylocentrotus. 
We find that the infolded funnel now becomes enlarged at the base 
into a chamber, and is attached to the outer wall of the embryo by sus- 
pensoria or filamentous bodies derived from the mesoblastic cells. Ex- 
teriorly the larva is truncated, flat on one side, more rounded in the 
diametrically opposite region. It is ciliated with fine long cilia, those 
on the pole opposite the blastopore being prominent. These longer cilia 
may be the same as the tuft opposite the blastopore mentioned by Pro- 
fessor Nachtrieb in Mellita, and by Prouhof in the gastrula of Doro- 
cidaris papillata. 'The morphological importance of these cilia has been 
magnified, although they may indicate one more likeness between the 
well known pilidium and the Echinoderm larva. The invaginated cells 
of the hypoblast are cylindrical, ciliated, and not yet differentiated into 
the walls of the cesophagus, stomach, and intestine. 
In a gastrula one day old, Pl. IV. figs. 1, 2; we observe that the 
invaginated pouch has extended to the opposite pole of the larva, and 
as it lengthens in this direction its free end slowly approaches the flat 
side of the gastrula, which side is that known as the ventral. It now 
bends still more to this region, and is met by a corresponding infolding 
from the ventral surface. The walls of this infolding break away, and 
form the future anus, v, of the stages immediately following the gas- 
trula, and probably the mouth of the pluteus. 
In a gastrula in which the opening had not broken through, Pl. IV. 
fig. 2, it was observed that the gastrula stomach, ach, sends out two 
horn-shaped cceca, which are similar to structures in other genera 
known as ‘“‘ water-tubes,” “ Enteroccelen” or “laterale Scheiben.” In 
* Op. cit. p. 48. 
+ Sur la forme larvaire du Dorocidaris papillata. Comp. Rend. ci. pp. 886-388. 
