3i8 



Charles Zeleny. 



Fig. i6 (x 216). 



Larvcc from Lower Quartets of the Eight-Cell Stage. 



A, larva (age:i=46 hours) from lower (?) quartet. Note large enteron and 

 absence of apical organ. B, larva (ager=46 hours) from lower quartet. C, 

 same larva rotated horizontally: Note solid enteron and absence of apical 

 organ. Ahte large archenteric ingrowth and absefice of apical organ in all cases. 



Fig. 17 (x 216). 

 Lan'cc from Portions of the Eight-Cell Stage. 



A, larva (age=:48 hours) from lateral four-cell group. Note presence of 

 both enteron and apical organ. B, same larva rotated horizontally. C, larva 

 (age=r:33 hours) from lateral four-cell group. Note presence of both enteron 

 and apical organ. D, larva (age^48 hours) from upper quartet plus two cells 

 of lower quartet. Note three apical organs, large blastocoele, small enteron 

 and two ectodermal invaginations at sides of enteron. 



