August 31, 1906.] 



SCIENCE. 



277 



fortunately the type of the yellow young is 

 left uncertain by my records in all except five 

 cases. Four of the five were clear yellows 

 and one a sooty yellow. 



The three yellow animals employed in these 

 matings, c? C, d* 3.1= and ? 32, evidently bore 

 chocolate as a recessive character, but not 

 black. For if black had been present as a 

 recessive character, it should have made its 

 appearance as an active character in half of 

 the young produced, but not one of the 44 

 young recorded in this table was black pig- 

 mented. It is perfectly clear, however, from 

 Cuenot's statement that black may be present 

 in a yellow mouse as a recessive character. 

 That statement is supported by the following 

 observation : 



A yellow female, ? 35, own sister to yellow 

 ? 32 previously mentioned, was mated with 

 the same chocolate male, c^49, with which 

 5 32 had been mated. She produced three 

 young, two of which were yellow pigmented, 

 and one hlacJc. The difference in the gametic 

 condition of these two sisters is readily ex- 

 plained. Their mother was an albino which 

 transmitted to each of them the dominant yel- 

 low which they manifested; their father was a 

 black animal which bore recessive the choco- 

 late character. Evidently he transmitted 

 black to ? 35, but chocolate to ? 32. Accord- 

 ingly the gametic formula of 2 35 was yellow 

 (black recessive), but that of $ 32 was yellow 

 (chocolate recessive). 



The chocolate male ((^49), like chocolate 

 mice in general (see Allen, 1904), transmitted 

 no pigment character other than chocolate. 

 Mated with three different chocolate females 

 he produced 11 young, all chocolate pig- 

 mented. He was mated likewise with three 

 black females, each of which bore chocolate 

 as a recessive character. These matings pro- 

 duced 4 black and 2 chocolate young. In no 

 other mating, except with yellow ? 35, did he 

 produce black pigmented young. 



Two matings were made between an albino 

 (bearing latent the yellow and chocolate char- 

 acters) and homozygous black individuals as 

 follows : 



Albino 

 Parent. 

 c?2.P 

 c?2.P 



Black 

 Parent. 

 X $1 

 X $1.3= 



Yellow 

 Young. 

 : 1 

 9, 



Black 



Y'oung. 



3 



1 



Totals, 



The expectation is equal numbers of yellow 

 and of black young, on the hypothesis that 

 yellow dominates both black and chocolate 

 and that black dominates chocolate. 



Another albino, own sister to c^ 2. 1'' and like 

 him bearing latent the yellow and the choco- 

 late characters, was mated with black indi- 

 viduals of the same family as those used in 

 the foregoing matings but bearing chocolate 

 as a recessive character. The result was as 

 follows : 



The expectation in this case is that young 

 of three sorts will be produced in the propor- 

 tions, 2 yellow, 1 black, 1 chocolate, which is 

 exactly realized in the totals obtained. 



A mating was likewise made between an 

 albino, c? A (father of the albinos c? 2.1^ and 

 $2.1" used in the two experiments just de- 

 scribed, and like them bearing latent the char- 

 acters yellow and chocolate) and a chocolate 

 female $ 3.2", used also in matings with yellow 

 c? C. This mating produced one yellow and 

 one chocolate young, three other young dying 

 before their coat pigments were developed. 



These various observations harmonize en- 

 tirely with the statements of Cuenot, showing 

 that in mice the order of dominance of the 

 three pigments of the hair is yellow, hlach, 

 chocolate, each dominating those which follow 

 it in the series, but being recessive in relation 

 to those which precede it. This order is the 

 more surprising because in rabbits and guinea- 

 pigs black is dominant over yellow. In guinea- 

 pigs black is dominant also over chocolate, 

 but in rabbits a pure chocolate is unknown. 



The occurrence of two distinct types of yel- 

 lows is a matter deserving further attention. 

 The sooty yellow type may evidently be hetero- 



