Page:Popular Science Monthly Volume 67.djvu/203

Rh Mendel found that in cross-breeding between alternative characters, one uniformly dominates in the offspring from its very nature, while the other disappears. Just as, when the two pieces of glass are held up together we see only the opaque one, the transparent one being invisible. Mendel called the character seen in the offspring dominant, the unseen one he called recessive. In rabbits, the gray pigmented or Belgian hare coat is dominant over the albino coat, the latter being recessive (unseen) in cross-bred animals. Similarly, in mice, guinea pigs, and even in man, mating of an albino with a pure, pigmented individual produces only pigmented offspring. In guinea-pigs the rosetted or rough coat is dominant over smooth (normal) coat (see

Fig. 6); and short coat is dominant over long (or angora) coat (Fig. 8). In rabbits, also, the normal or short coat dominates over the angora coat (Fig. 3), and the same is probably true in cats and goats as well.

Among guinea-pigs there occurs a series of alternative pigment types which show Mendelian relations one to another. If we write them in this order, (1) agouti (i. e., black ticked with yellow, the ancestral or wild type of coat), (2) black, (3) yellow, (4) albino, we may say that each is dominant over all which follow it, and recessive in relation to all which precede it. Thus agouti mated with black, yellow or albino gives only agouti offspring; black mated with yellow or albino gives either black or agouti, but never yellow or albino, while yellow dominates over the albino only. In man, a condition of