Experiments with other Mammals 101 



makes a distinction between recessive and latent characters. 

 Recessive characters are those that disappear in the Mendelian 

 sense when brought into contact with a dominant character. 

 This recessive character is transmitted distinct from the domi- 

 nant character in half the gametes of the hybrid. A latent 

 character is a "condition of inactivity in which a normally domi- 

 nant character may exist in a recessive individual or gamete." 

 This latter is illustrated by the latent pigment carried by ex- 

 tracted albinos. Cross-breeding is necessary to bring the latent 

 character to activity again. 



When elementary pigmented types, or so-called pure races, 

 of different colors are crossed, neither color dominates perfectly 

 in the offspring. For example, when a black individual is 

 mated with a red one, the offspring are blackish, but not so black 

 as the black parent, red being also present, although masked 

 somewhat by the black. The agouti type carries the three pig- 

 ments black, chocolate, and red-yellow. When crossed with 

 pure black it gave in one case one agouti and two black indi- 

 viduals. 



Agouti crossed with red gave four young, three of them agouti 

 spotted with red, one red spotted with agouti and white. Black 

 animals seem to contain always some red pigment, which may 

 appear when crossed with albinos. Red animals may, however, 

 be free from black. Red crossed with white gives results that 

 depend on the latent pigment characters borne by the albino, 

 so that black offspring may appear among the others. A case 

 of special interest is found in white animals with black eyes, 

 which are therefore not albinos. 1 They do not seem to be al- 

 binos but may contain recessive albinism. They arose from 

 spotted ancestors, and Castle regards them as spotted animals 

 themselves with the pigment spots obliterated except in the eyes. 

 These animals bred inter se or with albinos produce offspring 

 with colored patches of greater or less extent. Whether by selec- 

 tion the white animals with black eyes could be made into a fixed 

 race remains to be shown, and judging from what breeders of 



1 Two such animals appeared in Castle's experiments. 



