5 .«' 



Fig. 27. 

 Fig. -2~. Sections of the Egg of Styela, showing matura- 

 tion, fertilization and early cleavage; 1 P. S., first polar 

 spindle, p.b., polar bodies, <$N, sperm nucleus, $iV, egg 

 nucleus, p.l., peripheral layer of yellow protoplasm, Cr. 

 crescent of yellow protoplasm, A v A 9 anterior cells, B z , 

 B s , posterior cells of the 4-cell stage. In 1 the sperm nucleus 

 and centrosome are at the lower pole near the point of 



