COAT CIIARACTKHS IN GUINH A-PIGS A NO RABBITS. 25 



may ever be latent. Future investigations alone can decide this point. 

 A recessive character apparently reappears pure in half the gametes 

 formed by the hybrid dominant individual, and is present in all the 

 gametes formed by a recessive individual ; a latent character apparently 

 never regains its existence apart from the recessive (i. <?., becomes 

 active) until cross-breeding brings this about. Future investigations 

 may require further modification or even entire abandonment of these 

 definitions, but for the present I find them useful to express the results 

 of my experiments. 



Latency of pigment characters in albinos is particularly clear in 

 mice, as shown by the investigations of Cue 1 not ( : 03), Darbishire 

 ( : 04), and especially of Allen ( : 04). For albino mice are, so far as 

 known, wholly unpigmented, yet they ordinarily, perhaps always, 

 transmit latent pigment characters, either singly or in combinations 

 identical with those occurring in pigmented mice. Alike in guinea- 

 pigs and in mice, a clew to what pigment characters are latent in the 

 individual may often, though not always, be learned from a mere 

 knowledge of its parentage. Thus, in guinea-pigs, an albino born of 

 two red or yellow parents does not transmit latent black in any of its 

 gametes ; but one born of two black parents may or may not form 

 gametes transmitting red apart from black pigment. The reason for 

 this difference will be apparent when we come to consider the relation 

 of red and black to each other in cross-breeding. For the present I 

 would merely call attention to this case as showing that it is not the 

 ancestry of the albinos which governs the behavior of their gametes in 

 cross-breeding, as Darbishire ( .-04) maintains, but rather the existence 

 of pigment characters as distinct entities, though latent, in the gametes 

 formed by albinos. In certain cases we can, with confidence, predict 

 the absence of a pigment character, even in a latent condition, from 

 the gametes of an albino, viz, in cases where we know the pigmented 

 parents to have been free from that character. Thus an albino born of 

 red or yellow parents does not transmit black, because red or yellow 

 animals do not contain the black character either active or latent, and 

 so can not transmit it to their albino offspring. Where the parentage 

 is unknown, suitable breeding tests show with equal certainty (often the 

 production of as few as two young indicates clearly) what latent pigment 

 characters are transmitted by the albino. A particular pigment charac- 

 ter, when present latent in the gametes formed by an albino, appears 

 to be regularly present either (i) in all the gametes formed, or (2) in 

 half those formed, as suggested by the cases of albino c?cf 2002 and 

 635 already cited. No evidence exists of the occurrence of a latent 

 pigment character in other proportions of the gametes, as should be 

 the case on the " ancestry " idea of Darbishire. 



