DEVELOPMENT OF AMPIIIOXUS 



557 



Development of Amphioxus. The oosperm of Am- 

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



Fro. 141,— Stage? in the liegmentation of th_ oosperm o'i Amphioxus. 

 U, represents the four-celled stage (C) from above -^n, vertical section of G ■ K 

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

 Hatschek.) ' 



