The Cellular Basis 



1P.S. 



143 



B 3 



FIG. 46. SECTIONS OF THE EGG OF Styela, showing maturation, fertiliza- 

 tion and early cleavage, i PS., First polar spindle. />.&., Polar bodies; 

 $ N, sperm nucleus, $N, egg nucleus. />./., peripheral layer of yellow pro- 

 toplasm. Cr., Crescent of yellow protoplasm. A z , A 3 , Anterior cells, 

 B 3 , B 3 Posterior cells of the 4-cell stage. In i the sperm nucleus and cen- 



