346 ORILLA STOTLER WERNER. 



somes in the female is concerned with sex-linkage and finally to 

 account for the presence of a third non-homologous body which 

 must evidently be present. 



Sex-chromosomes carrying sex-linked characters are usually 

 among the largest of the complex. In the male of the Indian 

 runner duck, then, it is reasonable to suppose that the sex pair 

 would be among the largest if not the largest in the series. In 

 this series there are certainly six pairs that are sharply marked off 

 in size from the remaining thirty-one pairs. Among them again 

 three pairs may be distinguished as larger than the remaining 

 three, and the largest of these is a pair of J's which it might be 

 supposed are the sex pair. For the sake of argument, at least, 

 let us assume that 38Z is the sex pair (Figs. 37-42, number 38Z). 



Now, in the female the sex-chromosome concerned with sex- 

 linkage should be an unpaired body and similar in size and shape 

 to the sex pair in the male with the members of which it, of course, 

 would have to alternate. Evidently the largest chromosome 

 (W) can not be this body. If the sex-linked chromosomes in the 

 male are the largest in the series, as is usual in animals, in the 

 cells of the female we would of necessity look for a homolgue of 

 them among the largest in the series after the longest chromosome 

 (W) is ruled out. From the drawings it would seem that there 

 are four of these next largest chromosomes and they are very 

 much alike in size. Just what one of the four might function in 

 the capacity of a sex-linkage body is not possible to determine 

 now. It might be supposed, however, that, as in the male, it is 

 one of the largest (38Z). 



If that be the case there would then remain an unpaired 

 chromosome in the female to be taken from the remaining three 

 large chromosomes. This chromosome like the largest one (W) 

 in the female series would have no homologue in the male series 

 and of course would be limited to the female line and would be a 

 second w-chromosome (w). 



In the female complex, then, there would be a group of three 

 large chromosomes, one of which would be a sex-linked chromo- 

 some, homologous to and capable of alternating with the largest 

 sex-linked chromosomes in the male. The other two would be 

 chromosomes not concerned with sex-linkage and, since they 



