COLOUR INHERITANCE IN CATS. WITH SPECIAL 

 REFERENCE TO THE COLOURS BLACK. YEL 

 LOW AND TORTOISE-SHELL. 



hY i\ r. LITTLE. 



Research Associate. Carneijie SUition for K.rpei'imeutal Evolution 

 (CoM Spring HarlM)r, Now Y«)rk). 



I. Introductory. 



This paper has two <>hject«<: (1) the critical examination of exjKTi- 

 mentAl data on, and of current hyjK>theses concrrnin^ the inhi-ritaneo of 

 black, yellow, and t-ortoise-shell coat colours in cats; (2) the suggestion 

 of possible explanations for the occurrence of (a) unexi>ect<*d colour 

 classes in oniinary crosses between blacks, yellows, and t<^rtoise-shell8, 

 and of (6) both sterile and fertile tortoise-shell males which appt-ar 

 extremely rarely. 



The fact that the work of all investigators of this subject ha.s left 

 the two points above mentioned not Siitisfactorily accounted for justifies 

 an attempt to explain the observed experimental results, even though at 

 this time no additional breeding data are offered fijr consideration. 



IL The facts requiring explanation. 



The critical and apparently contradictory facts which have been 

 brought out by breeding experiments with cats, and which must bo 

 satisfactorily accounted for and explained, are brieHy jis folli)Ws: 



(1) In crosses between yellow imtles and black fe nudes, whon* the 

 expectiition on the b;isis of complete scx-linkagc is black males and 

 tortoise-.shell females, black females are sometimes produced. { I )oncaster, 

 1913.) 



(2) In cj'osses between yelloin males and tortoise-shell /enuiles, whi*re 

 yellow males, black mah's, yollow f.niah's and tort«»is('-sh»'ll fomalos are 

 the only chv-sses expoctod on tho b;i.sis of coiiiphto sox-linkai^i'. black- 

 females are sometimes produced. ( I )oncastoi\ 1 IM )i. ) 



