INHERITANCE OF PLUMAGE-COLOR. 17 



The experiments recorded in table 5 show that when the mottled 

 form is mated with a pure yellow or a pure green the offspring are 

 nearly equally of the two parental colors and none other.* Moreover, 

 the extracted yellows are "pure," since when bred inter se they pro- 

 duce only yellows. 



The interpretation of the results of breeding plumage-color is not 

 difficult and may easily be brought to accord with Mendel's law. As 

 already stated, yellow is "green" which has lost its melanic pigment. 

 The mottled canary further differs from the green or the yellow in a 

 spottedness like that of the spotted mouse; and as Cuenot (1903) has 

 shown the latter to be due to a particular factor we may expect the 

 same to be true for the canary. Calling the black factor N (nigrum) 

 and the mottling factor M y we may assign to the green parent the 

 gametic formula Nm and to the yellow parent the formula nM, i. e., it 

 contains the mottling factor, but lacks the melanin necessary to make 

 it show. The gametic composition of F! is thus NM nm and the soma 

 shows black in spots as a green on a background of yellow. On this 

 assumption of two pairs of allelomorphs, we expect in every 16 birds 

 of F 2 : 9 mottled, 3 green, and 4 yellow, of which last class 3 are nM 

 and 1 nm, without trace of the mottling factor. The observed result 

 in F 2 agrees fairly well with this hypothesis. When mottled is mated 

 with mottled we get, as table 4 shows, a total of 34 mottled, 6 green, 

 and 13 yellow, expectation being 30, 10, and 13 respectively. The 

 result departs from expectation in so far as there is a deficiency of 

 greens, but a change of 4 individuals from mottled to green would 

 establish complete accord with theory. 



When a mottled bird is mated with yellow or with green expecta- 

 tion is an equal number of mottled and self-colored offspring. The 

 number of offspring of each class derived from the mottled X yellow 

 cross accords with expectation. Of 62, 32 are mottled and 30 yellow. 

 Of 38 offspring of a mottled X green cross 22, or 58 per cent, were 

 mottled and 16 green. Here, again, is a deficiency of greens, but not 

 a very improbable one. Altogether, the results favor the hypothesis 

 that there are in canary plumage two distinct and distinguishing 

 factors a black factor and a mottling factor. 



2. INHERITANCE OF TICKING. 



It has been stated above that in mating yellow birds yellow off- 

 spring ticked with black were occasionally obtained. Similarly marked 

 birds were obtained at other times. It seemed desirable to ascertain 



* One clear exception and one doubtful one are found in the green X mottled 

 matings of Experiments 711 and 714 where a yellow appeared among the offspring. 



