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 kaun dieser Ansicht nicht beitreten die nach aussen 

 schlagenden Geisselendes Urdarms scheiueu den Eiutritt von fremden 

 Stoifeu durchaus zu verhindern." 



A. Agassiz says that in the starfish and Strongylocentrotus gastrula 

 currents of watef 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 Xachtrieb in jSIellita, and by Prouho f 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 oesophagus, stomach, and intestine. 



In a gastrula one day old, PI. 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 

 beuds still more to this region, and is met by a corresponding infolding 

 from the ventral surface. The walls of this infolding bi-eak 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, PI. IV. 

 fig. 2, it was observed that the gastrula stomach, ach, sends out two 

 horn-shaped coeca, which are similar to structures in other genera 

 known as "water-tubes," " Enterocoelen" or "laterale Scheiben." In 



* Op. cit. p. 48. 



t Sur la forme larvaire du Dorocidaris papillata. Comp. Rend. ci. pp. 386-388. 



