218 Mr Doncaster, On the Inheritance of Goat-colour in Rats. 



individuals, and (b) with the nature and relations of Crampe's 

 types 7, 6, and 5. 



It has been shown by Cuenot*", and others in mice, and more 

 recently by Hurst j" in rabbits, that albinos are not all similar in 

 constitution, but that when mated with a given coloured individual 

 their offspring differ according to the origin of the albino parent. 

 I find that this is also the case in rats ; some albinos carry the 

 determinant for brown, others black, and others again both brown 

 and black. So also with pattern ; some carry the piebald character, 

 some the " self" (or " Irish "). An albino can best be tested in 

 these respects by mating it with a black-and-white, since black is 

 recessive to brown and the pied character to " self." Experiments 

 showing the results of such matings are Nos. 32, 33, 41, 45, 

 58 a and b, and, with regard to colour only, Nos. 2, 37, 57. Black- 

 and-whites paired together can give nothing but black-and-white 

 and albino, but when paired with an albino carrying brown and 

 " self" determinants, brown self-coloured rats are produced. In 

 Exps. 32 and 41 the albino used contained only black and " pie," so 

 that only black-and-white and albino young appeared, roughly 

 in equal numbers. In Exp. 33 the albino, although of similar 

 ancestry to those used in Exps. 32 and 41, carried only the. "self" 

 character as far as pattern is concerned, but both black and 

 brown colour determinants, so that of the coloured young all were 

 self-coloured (with white patch on the underside), 4 being brown 

 and 5 black. In Exp. 45 the albino, derived from two "Irish" 

 parents, carried the black colour determinant and the "self" 

 character, and all the coloured young were "Irish." 



Similar results are seen in Exps. 2 and 37, in the first of 

 which the albino bore only black, in the second both black and 

 brown, giving 4 brown young to 6 " Irish." It is therefore quite 

 clear that as in other animals the albinos, although giving nothing 

 but albino when paired together (Exp. 46), differ from one another 

 in constitution, and influence their young both in colour and 

 pattern. In this connexion it is of interest that HaackeJ describes 

 an albino rat in which the hair of the hood and back-stripe 

 differed from the rest in texture, although quite without pigment. 

 Such an animal would doubtless have been found to bear the 

 piebald character only, had it been tested by mating with a black- 

 and-white. 



The second point to which my attention has been chiefly 



directed concerns the relations between the different forms of 



pattern, particularly the nature of Crampe's types 2 and 6 and 



their relation to the pure self-coloured and pied forms respectively. 



* Arch. Zool. Exp. and Gen. Notes and Eev. Ser. 4, t. 2, 1904, p. xlv. 

 t Journ. Linn. Soc. Zool., Vol. xxix. p. 283. 



J Haacke, Biol. Centralbl. xv. 1895, p. 63. " Wesen, Ursachen und Vererbung 

 v. Albinismus etc." 



