Localization of the Nemertine Egg. 



V 



303 



V 

 Fig. 6 (x 180). 



Diagram of Egg Soon After Fertilization and Before the Fai-mation of the First Polar 



Body. 

 The dotted line at one pole incloses a clear area containing the first polar 

 spindle. The basal protuberance is still very prominent; HH, VV and OO 

 represent, respectively, the directions of the horizontal, vertical and oblique 

 cuts. 



Fig. 7 (x 180). 

 Diagram of Egg with One Polar Body. 

 The basal protuberance is still evident, but not as prominent as in the for- 

 mer stages; HH, VV and OO represent, respectively, the directions of the 

 horizontal, vertical and oblique cuts. 



at least as far as the present experiments go. The most common 

 irregularity is a simple departure from the normal division rhythm 

 (Fig, 8D), which in other cases is accompanied by a displacement 

 of some of the cells (Figs. 8 A, B, C). An interesting plate form 

 was obtained from a vertical fragment (Figs. BE, F, G). Its 

 special interest comes from the fact that notwithstanding the ir- 

 regularity it formed a SAvimming larva on the second day, 24 

 hours after fertilization. 



