70 



BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



CLEAVAGE OF APLYSIA. 

 Blochmann ('83). 



In the above table the labelling of cells indicated in the second col- 

 umn is that given by Blochmann to cells which seem to be homologous 

 with those of quadrant A. 



The cleavage of Aplysia, so far as followed by Blochmann, resembles 

 very closely that of Umbrella. If we interpret the cleavage as Heymons 

 has that of Umbrella, we find that here also the posterior and smaller 

 cell of the two-cell stage divides first; the mesoderm quadrant D 



