CROSSING-OVER 135 



gave KY 20 5J:28$$ and 10 KK ?? without a trace of 

 the YY pattern. The other F, KK female, which had 

 given 41 offspring parthenogeneticallv, when mated to a 

 KM male, gave KK 7 5$: 6$?, and KM 13$$: 10?$. It 

 is obviously impossible to determine if all the KK off- 

 spring from this mating were produced bisexually, or 

 some of them parthenogenetically. However, since par- 

 then ogenetically produced individuals are, with rare ex- 

 ceptions, females, the result is somewhat checked by the 

 proportion of 7 5$: 6$?. From the 68 F., offspring sev- 

 eral females were allowed to reproduce without exposure 

 to males of any kind at any tinu>, and IC).". KK females 

 resulted in F,*. From the 41 KK V, individuals one 

 which had never associated with any male gave 40 KK 

 females in F^, and another, a 



KK and YY. 



