268 



GERM-CELL CYCLE IN ANIMALS 



hence the spermatozoa simply initiate development. 

 The chromosome cycle of Rhabditis nigrovenosa has 

 been studied by Boveri (1911) and Schleip (1911). 



rHYLLOXERA CARYMCAVLJS 



T'cCiA. T'^:cac^ A A Q\ 



*y«rrut/ t^ ft2ft^eii -^sn. 



o 





o 



i 



C^D 



c:rP 



o 







1 



<Seouu(/ J^/z/ey yO Ik^ 



o 



10 



Ti'^a/f Sfii/ruiU. 



\ 



o ) j-^^ 



Sf>t/mtalcaftc 



Fig. 72. — Chromosome cycle in Phylloxera carycBcaulis. (From Mor- 

 gan's Heredity and Sex, published by the Columbia University Press.) 



