PARTHENOGENESIS 



181 



bring this case into line with the rest of our informa- 

 tion bearing on the relation of the chromosomes to sex. 

 One important point still remains to be explained. 

 What causes some of the migrants to produce large 



PHYLLOXERA CAKYJECAULJS 



<Stem TtlcthvCI 44Q 



o 





O 



O 



Cd 



<C? 



O 











11,8 N 



@> 



O 

 Q 







(J -eaa 



"> J TvtsC 

 Sfizvmatcci/tt 



StccneL 



Fig. 93. — Chromosomal cycle of P. carycecaulis. 



