10 



INHERITANCE OF COAT-PIGMENTS AND COAT-PATTERNS 



The evidence contained in tables 2 and 3 (pp. 35, 36), is presented in the form 

 of summaries only. To give an idea of the sources from which it was obtained, 

 a genealogy may be considered in detail (fig. i). 



Wild, 



4 rr 



cf Wild, white 

 \ 



<S 12.W/BHJ 



Ai, Gl(-) 

 I 



j? 34, GI(W-BH) 



, G-I(W-BH) 



FIG. 1. 



A wild gray female and a wild white male were trapped together. Nothing 

 is known of their ancestry, but they were probably derived from escaped 

 tame albinos which had mated with wild gray rats. This pair of captured 

 rats produced gray Irish young, two of which (Ai and A 2 ), when mated with 

 ordinary albinos, produced gray Irish young which bore, as recessive char- 

 acters, total albinism, black pigmentation, and the hooded pattern. Two 

 of these triple heterozygotes ( $ 34 and cT 1 6) were now mated together 

 and produced a litter of seven young (141-147, fig. i), which were tested 

 as to their gametic condition, with the results indicated in fig. i. Five of 

 the 7 were gray pigmented and 2 black, but no two were alike in gametic 

 character. Males 146 and 147 were mated with black hooded females and 

 with albino females of black hooded parentage, producing nothing but hooded 

 young. This result showed that they bore no coat-pattern except the hooded 

 one, and were free from recessive albinism. 



The young of ^147 were all black pigmented, showing that animal to 

 be entirely homozygous, but some of the young of 6^146 were gray pig- 

 mented, some black pigmented, showing that he bore black pigmentation 

 as a recessive character, being otherwise homozygous. 



