Localization of the Nemertine Egg. 



317 



Fig. 15 (x 216). 



Larva from U[^pcr Quartets of the Eight-Cell Stage. 



A, larva (age^44 hours) from complete upper quartet. B, larva (age 

 =:4S hours) from upper quartet, with one cell injured. C, same larva rotated 

 horizontally. D, larva (age^45 hours) from complete upper quartet. The 

 egg already showed the cell constrictions for the next (i6-cell) division. E, 

 same larva rotated horizontally. F, larva (age:=45 hours) from complete 

 upper quartet. The inner cell mass does not connect with the side of the 

 larva (i. e., it is free). G, larva (ager=23 hours) from complete upper quartet. 

 H, larva (age:=33 hours) from isolated blastomere of the upper quartet. I. 

 double larva (age=46 hours) from upper (?) quartet. Note presence of apical 

 organ and absence oi enteron in Numbers A to F. 



