Page:Popular Science Monthly Volume 67.djvu/208

202 Considering pigmentation and hair-length separately, we see, first, that there are 12 pigmented animals to 4 albinos, or 3 to 1, as expected; and, secondly, that there are 12 short-haired to 4 long-haired animals, again 3 dominants to 1 recessive. But if we consider the relation of each pair of characters to the other, we find absolutely no correlation between them. Albinism may or may not be associated with long hair, and pigmented coat may or may not be associated with short coat in the offspring, though they were so associated in the grandparents. As a matter of fact, when the animals are tested one by one, to determine the presence of recessive characters, we find that albinism, visibly present in 4 out of 16 offspring, is present recessive in 1 others, and that in half

of these cases it is associated with short coat, while in the other half it is associated with long coat.

In another experiment which I have performed with guinea-pigs, a cross was made involving three pairs of alternative coat-characters, length, pigmentation and roughness of coat. A long-haired rough albino (Fig. 4) was mated with short-haired smooth pigmented animals (Fig. 5). The young were all short-haired, rough and pigmented (Fig. 6). The coat-characters seen in these offspring are the three dominant characters, two of which were received from one parent, one from the other; the three alternative recessive characters are present but unseen.

When the young were bred together, they produced offspring of eight different sorts, including all possible combinations of the three pairs of alternative characters.