DEPARTMENT OF GENETICS. 127 



that the genetic factors received in the gamete from the Japanese 

 parent were sufficient to cause the Fi hybrids to react favorably to 

 Japanese-mouse tissue. 



The same situation should be found to exist with reference to splenic 

 implants. The Fi hybrids between Japanese mice and albinos should 

 grow implants of the Japanese-mouse spleen quite as successfully as 

 they grow their own. On the other hand, the Japanese mice should 

 grow implants of their own spleens, but should eliminate those from 

 Fi mice, since they contain none of the complex of genetic factors which 

 characterize the albino race, and which are in some degree present in 

 the Fi animals. 



Actually, this is found to be the case. 33 Fi mice inoculated simul- 

 taneously with their own and with Japanese waltzing-mouse spleen 

 grew both implants successfully, as expected; 23 Japanese mice, 20 days 

 after inoculation, were growing the implants of their own spleen, but 

 had eliminated or were eliminating the implants of Fi spleen. 



This completes satisfactorily the first experiment of a series designed 

 to obtain evidence concerning the nature and method of inheritance 

 of the genetic factors underlying the physiological differences between 

 individual mammals. L. Loeb has recently advanced an hypothesis of 

 "auto-syngenesio-, homoio-, and species-individuality differentials" 

 to explain somewhat similar cases. The work here reported indicates 

 strongly that a simpler and more consistent explanation exists. 



Histological preparations confirmatory of the macroscopic observa- 

 tions of the transplanted tissues have been obtained by Mr. W. F. 

 Windle, of Denison University, working during the summer with Dr. 

 Little. Three papers covering this series of experiments from genetic, 

 medical, and histological viewpoints are now in preparation. 



Genetic Studies in Cats. 



In 1920, Doncaster suggested that the occurrence of tortoise-shell 

 males in cats and their usual sterility might be due to a process of 

 hormone action somewhat similar to that involved in the production 

 of free martins in cattle. During the past year, through the courtesy 

 of the Society for the Prevention of Cruelty to Animals in New York 

 City, it has been possible for Miss E. E. Jones to examine the uteri 

 of 140 pregnant female cats. In a total of 589 embryos, no sign of 

 anastomosis of the circulatory systems supplying the fetuses has been 

 discerned. The work provides a considerable body of negative evi- 

 dence against the correctness of Doncaster's hypothesis. 



White coat color in cats has for some time been recognized as a 

 probable Mendelian dominant representing an extreme form of spotting. 

 Since a factor with somewhat the same function in mice has been 

 found by Little (1915) to behave as a lethal when present in a duplex 

 condition, it was thought to be worth while to determine whether there 



