January 15, 1904.] 



SCIENCE. 



Ill 



doubtful case where white mice produced col- 

 ored offspring. In two crosses of white par- 

 ents I got nine offspring; all were white. 



11. Yelloiu X Yellow.— 1. Yellow-red (8)* X 

 yellow-red (Y). The mother (8) was yellow- 

 red with a patch of white below; the father 

 was pure yellow-red. Of the offspring one 

 was pure yellow-red like the father, two were 

 brownish yellow above and much lighter below, 

 one was brownish red with patches of white, 

 and five were chocolate with yellow flanks and 

 patches of white above and below. Thus, one 

 bred true to the father but tjie remainder were 

 much darker and had a mixture of colors. 



(f white (6) \ 

 ^'{yellow (7) )X^'^^°^ 



(7). Of the four offspring one was a uniform 

 light yellow (57) ; one was yellow above and 

 white below and on the flanks (59) ; one was 

 dirty yellow above, white below (58) ; and the 

 last was wild-mouse gray (or agouti) above 

 and white on belly and flanks. The result in 

 both cases is seen to be very variable. 



ni. Blach (g) and Blaclc (g).— My blacks 

 seemed delicate and relatively infertile, so that 

 of two crosses only two individuals ■ survived 

 • — ^both were black. Black behaves something 

 like albinism. Is it not likewise recessive? 



IV. Chocolate X Chocolate. — Chocolate is a 

 broad class including various shades of color 

 from a dark red-gray to a dark red-yellow. 

 I raised four families as follows : 1 and 2. 

 Chocolate (10) X Chocolate (1) with nine 

 offspring, as follows : Uniform chocolate, nos. 

 22, 23, 26, 66 and 65. Chocolate above, more 

 or less white below, nos. 67, 68. Chocolate 

 with white spots, nos. 24, 25. 



3. Chocolate (66 | W Chocolate (ss ] \. 



These full siblingsf of chocolate parents pro- 

 duced five offspring. All were of a uniform 

 chocolate color. 



4. Chocolate ^67 I )x Chocolate ^25 P^j. 



* The numbers in parentheses are those of Ihe 

 pedigree mice. 



t Sibling (Pearson) is a term applicable either 

 to brother or to sister. 



There was only one survivor of this pair; it 

 was chocolate colored excepting for some white 

 on the belly. 



Thus the chocolate color shows itself rather 

 stable, especially in the second pure bred gen- 

 eration. 



B. THE OFFSPRING OF MICE OF DIFFERENT COLOR. 



I. Gray and White. — This cross has been 

 made by several investigators, as indicated 

 above. The usual result is that the offspring 

 in the first filial (mongrel) generation (F^ in 

 Bateson's nomenclature) are prevailingly gray 

 like the wild house mouse. My own experi- 

 ence is partly confirmatory. 



A wild house mouse (15) X albino (5) gave 

 five offspring : nos. 47 to 51. Four of these 

 resembled the wild mother in coat excepting 

 that they were yellower on the back of the 

 neck and of a cream color in the region be- 

 tween the fore legs and also between the hind 

 legs. Also the coat had a richer, glossier look 

 than the mother's. The other one of the off- 

 spring was generally agouti above and ashy 

 below, but the hairs of the ventral part of the 

 shoulder girdle were yellow tipped, there was a 

 mid-ventral white patch and there were five 

 distinct white patches on the dorsal side. 

 These were unlike anything in the mother, and 

 indicated particulate inheritance by the mon- 

 grel from both parents, but especially from the 

 mother. My results agree with those of 

 Crampe, who found that similarly bred rats 

 give in F, either uniformly gray or gray and 

 white. Darbishire (1903) crossing walzers 

 and albinos finds that the mongrels have the 

 less white the purer bred the albinos are, and 

 von Guaita's pure-bred albinos gave all gray 

 offsjiring when crossed with walzers. I know 

 nothing of the ancestry of the albino (5) ; but 

 it may be inferred that it was not pure bred. 

 With an albino that had been bred pure for 

 two generations I got the following result: 



Gray I 



54 



21, chocolate (10 X 1) 

 29, house 



(( 4, white \ 

 ^M 5. white)- 



Five offspring were obtained all gray like a 



