The Cellular Basis 189 



male (Fig. 62, P) all the females of the F t generation are red- 

 eyed and all the males white-eyed ("criss-cross" inheritance) and 

 if these are interbred there are produced in the F 2 generation 

 equal numbers of red-eyed and white-eyed males and females 

 (Fig. 62). 



The distribution of the maternal and paternal sex chromo- 

 somes exactly parallels this distribution of this sex-linked char- 

 acter, as is shown in Figs. 61 and 62, and this proves that the 

 differential factors for these characters are carried in these sex 

 chromosomes. 



By a series of ingenious experiments Foot and Strobell have 

 shown that the differential factors for certain sex-limited char- 

 acters in insects, that is, characters which are limited to one sex, 

 are not contained in the "sex chromosomes," and they argue that 

 the differential factors for sex and for sex-linked characters can- 

 not be located in these chromosomes. Their conclusions apply 

 only to sex-limited and not to sex-linked characters. There is 



Chromosomes 



XX Parents 



9 



^M 



Gametes 



<Q> 



Gametes 



FIG. 64. DIAGRAM OF INHERITANCE OF COLOR BLINDNESS THROUGH THE 

 FEMALE. A color blind female transmits her defects to all her sons, to 

 half of her granddaughters and to half of her grandsons. Corresponding 

 distribution of" sex chromosomes on right. (After Morgan.) 



