xiv] SEX-LIMITED INHERITANCE 231 



among Mammals, it is of the kind in which the male trans- 

 mits certain features only to his daughters, while in Lepido- 

 ptera and Birds the converse condition exists in which the 

 female transmits characters only to her sons. In each case, 

 therefore, the sex in which one chromosome is either un- 

 paired, or has a dissimilar mate, transmits certain characters 

 only to the opposite sex, exactly as the odd chromosome 

 is transmitted to offspring of the other sex. In Drosophila, 

 for example, a red-eyed, normal-winged male mated to a 

 white-eyed, rudimentary-winged female has red-eyed nor- 

 mal-winged daughters and white-eyed, rudimentary-winged 

 sons. The transmission of these two characters thus corre- 

 sponds with the fact that the male transmits the ^f -chromo- 

 some only to his daughters. In the converse cross of red- 

 eyed, normal female by white, rudimentary male, all the 

 offspring of both sexes are red-eyed and normal-winged, 

 since the female transmits an X-chromosome, which by 

 hypothesis bears these characters, to her offspring of both 

 sexes. Similarly in Man, the male transmits the factor for 

 normal vision as contrasted with colour-blindness only to 

 his daughters, and in the Cat the male transmits the orange 

 colour in the same way, and it has been found that in several 

 Mammals, including Man and the Cat 1 , an unpaired X- 

 chromosome exists in the male and is therefore transmitted 

 by him only to his female offspring. 



In the Moth Abraxas, on the other hand, the conditions 

 are reversed. A female of the type form mated with a 

 lacticolor male has sons of the type form and lacticolor 

 daughters, so that in this species the female transmits the 

 type character only to her sons, while in the converse cross 

 the male transmits the same character to both sons and 

 daughters And correspondingly in some races of this moth 



1 VON WlNlWARTER, 1912, 1914. 



