88 Experimental Zoology 
“pure” race was not pure, since it may produce some albinos 
when paired with albinos. 
Allen has also carried out a large number of experiments with 
mice. Crossing the gray house mouse with the albino gave 
gray offspring, as most other experimenters have found. The 
second generation (F,) gave approximately the Mendelian ratio 
of three grays to one white, the former being partly pure grays, 
partly mixed. Crossing the dominant recessives (heterozygote) 
with the extracted albinos, where equality of grays and whites 
would be expected, gave 84 pigmented young and 64 whites. 
While there is only an approximation to equality here (74 of 
each expected), the deficiency in white may be due to insuf- 
ficiency of numbers, but possibly to some other factor. Allen 
found that when spotted mice were bred to albinos the off- 
spring were spotted, — often with Jess white than the original 
spotted parent, — and in some cases the white almost, or even 
completely, disappeared. Thus, although we may look upon 
the spotted condition as a unit-character that is dominant, its 
extent appears to be variable. In fact, a latent character may 
also come to light here that is not seen in either parent, but must 
be potential in one or in both of them. While the white parent 
might have been expected to add more white to the offspring, — 
on Galton’s hypothesis, — the result is exactly the opposite. 
When pigmented, heterozygote individuals (Ff) were inbred, 
they produced 159 pigmented young and 55 albinos (53.5 being 
the Mendelian expectation). In another experiment, pig- 
mented, heterozygote individuals (F,) were bred to pure albi- 
nos, giving 69 pigmented and 69 albinos, exactly the anticipated 
ratio. 
Allen carried out a number of experiments made to test the 
inheritance of partial albinism, as he calls the condition when 
white areas are present along with colored areas. When ‘‘par- 
tial albinos” are bred to pure albinos, the young (F,) were more 
nearly totally pigmented (as stated above), some showing no 
trace of white, others had white toes, or a white tip to the tail 
or even a few scattered white hairs. One only had a white spot 
