RESULTS OF HYBRIDIZING RING-DOVES. 



FI dominant males. 

 DR cf cf 



2. Recessive cf 



composition RR cf cf 

 gametes all R a 71 



FI dominant males. 

 DR cf cf 



3. Dominant FI cf 



composition DR cf cf 

 gametes D cf 



R cf 



dominant males. 



DR cf cf 



recessive males. 



RR cf cf 

 I cf 

 composition DR cf cf 



D cf 

 gametes R cf 



dominant males. 

 result DD cf cf 

 a/50 



result 



4. Dominant 



dominant females. 

 DR 9 cf 

 Dominant 9 . 

 DR 9 cf 

 R 9 

 D cf 



recessive females. 

 RR 9 cf 



X Recessive 9 . 



RR 9 cf 

 R 9 

 R cf 



dominant females. 

 DR 9 cf 

 recessive females. 

 RR 9 cf 

 Dominant 9 . 

 DR 9 cf 

 R 9 

 D cf 



dominant females. 

 DR 9 cf 



I recessive females. 



DR cf cf RR 9 cf 



If, however, the female is regarded as homozygous for sex and 

 also for somatic characters, and the male as heterozygous for sex, 

 these phenomena may be explained in my judgment with the fol- 

 lowing additional assumption : that the female producing sperms 

 of the recessive male have the power of suppressing or checking the 

 development of dominant characteristics which may be carried 

 by the egg or it may be that these sperms lack something which 

 is necessary for the development of the dominant characters. 

 This position is supported by all of the cytological evidence known 

 to me, and it is not inconsistent with the idea that potentialities 

 of both sexes may be present in both male and female gametes 

 as well as in zygotes if such is the case. The castration experi- 

 ments of Goodale ('10), for instance, have demonstrated that 

 some female birds at least may develop male characteristics when 



