No. 584] SHORT Eli ARTICLES AXD DISCUSSIONS 519 



ther objection to this hypothesis inasmuch as it is not explained 

 how gamete bX differs from BX. Doncaster admits these diffi- 

 culties, staling that further work is necessary before a definite 

 conclusion can be reached. 



In a more recent paper 1 Doncaster has suggested non-disjunc- 

 tion of the sex-chromosomes in oogenesis as a possible explana- 

 tion. This explains the matroclinous black females, but fails to 

 account for the lack of an equal number of patroelinous yellow 

 males. It also fails to account for the tortoiseshell male and 

 the occurrence of tortoiseshell females among the offspring of 

 yellow by yellow. 



In a series of experiments begun upon cats at the University 

 of Pennsylvania during the last year, the tortoiseshell problem 

 has been especially investigated. A yellow Persian male was 

 crossed with common cats— black, maltese and tabby. The re- 

 sults, although not at present extensive, are sufficient to explain, 

 at least in part, the anomalies observed, and to surest a simple 

 explanation for the occurrence of unexpected classes. 



When the yellow male was crossed with a maltese female, a 

 maltese male and two blue and cream females were produced. 

 The blue and .-ream is the maltese or dilute tortoiseshell.^ When 



dilute kittens. This shows that the black female was hetero- 

 zygous for dilution. Two of the males were black and two mal- 

 tese. The two females were dark tortoiseshell. When the yel- 

 low male was crossed with a dark tabby, there were produced 

 dark and light tabbies and maltese. Blacks are also to be ex- 



fween tabby and blac/and between black and maltese. The 



yellow except for tabby striping. 

 The female offspring obtained fr( 



