DEVELOPMENT OF AMPIIIOXUS 



557 



Development of Amphioxns. The oosperm of Am- 

 phioxus (Fig. 141, A) undergoes binary fission (B), each 



Fig. 141.— Stages in the .segmentation of th. oosperm of Amphioxus. 

 a, represents the foitr-celled stage (C) from above ;')H, vertical section of G : K 

 vertical section of the blastula stage (I). (From Korschelt and Heidei, after 

 Hatschek.) _ 



