76 



INHERITANCE IN GUINEA-PIGS. 



BB stock. A stock consisting exclusively of very intense blacks. 

 No red or white spotting has been observed among them. Unfortu- 

 nately it is a stock of low fertility, and could not be used much to 

 advantage. 



BW stock. This stock has for years consisted exclusively of very 

 intense blacks and very sooty albinos. The blacks occasionally show 

 a few red hairs or a small red patch. This has been an extremely 

 useful stock, among other things, furnishing albinos known to be geneti- 

 cally identical with blacks, except for the albino factor. (Race B of 

 Parti.) 



Four-toe stock. This is a much-inbred stock, practically all the indi- 

 viduals of which show four good toes on the hind feet instead of the 

 normal three. This stock was developed by selection and inbreeding 

 by Professor Castle (Castle, 1906). Most of the individuals are a dull 

 black with dull red blotching and brindling and often with white spots. 

 Albinos appear quite frequently and reds much more rarely. 



TABLE 34. Genetic formula of stocks. 



In the tricolor stock the fur is typically a patchwork of red, white, and 

 black. Full-roughs, partial-roughs, and smooths occur among them. 

 The writer has used many guinea-pigs of very mongrel ancestry, which, 

 however, owe their partial rough coat to this stock. 



The sepia-and-cream and brown-eyed cream stocks have been selected 

 for years for extreme dilution. The former stock consists exclusively 

 of sepias, black-eyed yellows and creams, and albinos. The latter 

 consists exclusively of brown-eyed yellows and creams and albinos. 

 (Race C of Part I.) In the tables, these together are called dilute- 

 selection stock. 



Table 34 shows the Mendelian factors affecting color and roughness 

 of fur which occur in each stock. Unanalyzed hereditary conditions 

 which affect color and roughness are also included, prefixed by the 

 symbol S. Sw and Sy, as has already been stated, mean hereditary 



