IP.S. 



Fig. 2T. 

 Fig. 27. Sections or the Egg of Styela, showing matura- 

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

 spindle, p.b., polar bodies, (JiV, sperm nucleus, 5-^, egg 

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

 crescent of yellow protoplasm, A^, A^, anterior cells, B^ 

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

 and centrosome are at the lower pole near the point of 



