314 D . D. WHITNEY. 



Shull and after fertilization always develop into females but 

 neve*r into males. Thus the fertilization causes a change of the 



'08 Ueber die Bildung der Sexualzellen bei Aphididae. Zool. Anz., Vol. 33. 

 Gruvel, A. 



'05 Journ. Roy. Micro. Soc., p. 34. 



