1P.S 



FIG. 27. 



FIG. 27. SECTIONS OF THE EGG OF Styela, showing matura- 

 tion, fertilization and early cleavage; 1 P. 8., first polar 

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

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

 crescent of yellow protoplasm, Ap A v anterior cells, B 3 , 

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

 and centrosome are at the lower pole near the point of 



