268 



THE AMEBICAN NATURALIST [Vol. LIIT 



four Siamese which are "blue-pointed," presumably as a re- 

 sult of crosses with maltese, which are blue pigmented. An 

 exactly similar combination I have recently secured in crossing 

 rabbits, obtaining Hiraalayans with blue points in Fo from a 

 cross between ordinary black-pointed Himalayans and a self- 

 colored rabbit which carried blue as a recessive character. 



To summarize, we have the following indications that Siamese 

 coloration in cats is a form of true albinism similar to that of 

 the Himalayan rabbit, and still more closely resembling the 

 ruby-eyed rat and the red-eyed guinea-pig, all of which species 

 possess also more typical forms of albinism, but which are allelo- 

 morphs of those mentioned. 



(1) Siamese coloration in cats is attended by a deficiency in 

 amount of pigmentation in both coat and eye. (2) Yellow pig- 

 ment is more affected than black or brown pigment. (3) The 

 pigmentation is less at birth than at a later period. (4) The 

 character is recessive in heredity. (5) It is distinct from 

 "blue" dilution since it can be combined with it by suitable 

 crosses. 



Siamese in cats as far as reported occurs only in a non-agouti 

 form, as does Himalayan in rabbits bred for exhibition. But 

 by a cross with agouti rabbits, Himalayan rabbits are obtained 

 in F, which have agouti points. As this makes the contrast of 

 points with body less strong, fanciers' standards do not recog- 

 nize the combination. Nevertheless the experiment shows agouti 

 to be due to a genetic factor distinct from Himalayan. If Sia- 

 mese in cats is also distinct from agouti, it may be expected that 

 a cross of Siamese with tabby would produce Siamese tabbies in 

 F^, though the combination would probably not be pleasing to 

 the fancier. 



W. E. Castle. 



RrSSEY INSTITI TION. 



BIBLIOGRAPHY 



