OTHER METHODS OF SEX-DETERMINATION 223 



and none of them show any characters of males of the 

 maternal grandmother's race. The F 3 and F 4 males are 

 again all like those of the paternal forefather. There 

 seems to be here no Mendelian splitting for any charac- 

 ters that might have been expected to have come through 

 the maternal grandparent. 



crossover! 



Fig. 128. 

 Diagram illustrating the inheritance of a sex-linked character in 

 fish, carried both by the X- and the " Y-chromosome. " After 

 Winge.) 



The same results are obtained when the reciprocal 

 cross is made; the sons and grandsons are all like the 

 paternal parent, etc. 



In another fish, Aplocheilus latipes, inhabiting small 

 streams and paddy fields of Japan, several types differ- 

 ing in color are found. Other types have also appeared in 

 cultures. In these fish both males and females of each 

 type occur. Aida has shown that several of these differ- 

 ences are transmitted through the sex-chromosomes (both 

 X and Y). The genetic transmission of these characters 

 can be explained on the hypothesis that the genes are 

 carried sometimes in the Y- and sometimes in the X- 



