102 



Varietäten, Descendenz, Hybriden. 



by Prof. Pearson upon bis (Darbishire's) paper "An Experimental 

 Estjmation of the Theory of Ancestral Contributions" (Roy. Soc. 

 Proc. B. LXXXI. 1909.) 



R. P. Gregory. 



Sollas, I. B. J. Inheritance of Colour and of Supernume- 

 rary Mammae in Guinea Pigs, with a note on the occur- 

 , rence of a Dwarf form. (Rep. Evol. Comm. Roy. Soc. London. 

 V. p. 51—79, 1909.) 



The colour varieties in Guinea-Pigs fall into two main divisions, 

 characterized the one by a dark eye, the other by a ruby eye. The 

 dark-eyed forms always contain some black pigment, .while the 

 ruby^e3''ed possess chocolate pigment onl^^ In both groups there are 

 differences in the degree of pigmentation. The types included in 

 each group form corresponding series, as shown in the table, each 

 type being epistatic to those beneath it in the colum : 



Dark-eyed series. 



Rub3^-eyed series. 



Dense. 



Dilute. 



Dense. 



Dilute. 



The scheme of factors proposed is as follows: 

 G a factor determining the ticking of the hairs, (as in the iVgouti). 

 B „ „ „ black pigment in the eye and skin. 



R „ „ „ red pigment in the hair, and red and 



chocolate pigment in the skin and eye. 

 Ch „ „ „ chocolate pigment in the hair, skin 



and eye. 

 C „ „ „ Colour. 



The Constitution of the different varieties according to this scheme 

 is as follows: 



Variety. 



Factors. 



B 



R 



Ch 



Agouti .... 

 Black .... 

 Red, dark-eyed 

 Cinnamon . . 

 Chocolate . . . 

 Red, ruby-eyed 



X 

 X 

 X 

 X 

 X 

 X 



(It will be noticed that all the types are shown as possessing 

 R. Ref.) 



Albinos have the same Constitution as the coloured form from 

 which they are extracted, except for the absence of C. The albino 

 Guinea-Pig has coloured points, and is therefore not entirely devoid 



