Page:Popular Science Monthly Volume 67.djvu/209

Rh One large class was like the parents, short-haired, rough and pigmented. Two other classes were like the grand-parents, viz, shorthaired smooth pigmented, and long-haired rough albino. In addition, there were five other new classes not represented among the parents or grandparents. These were: short-haired rough albino (Fig. 11), short-haired smooth albino (Fig. 9), long-haired smooth albino (Fig. 7), long-haired smooth pigmented (Fig. 10), and long-haired rough pigmented (Fig. 12).

The eight classes of young produced in this experiment are not all equally numerous. The largest class is that which contains the three dominant characters (Fig. 6), the smallest that which contains the

three recessive characters (Fig. 7). Theoretically, they should number 27 individuals and 1 individual, respectively, in a total of 6-1 young. These proportions are roughly approximated in the observed result.

This experiment illustrates two important principles in heredity: First, if as regards the hair alone there exists such a variety of characters separately heritable, how great must be the number of such characters in the body as a whole, and how remote the probability that any animal will in all characters resemble any individual ancestor, provided that in a considerable number of heritable characters a choice is offered between 1 alternative conditions. Secondly, the experiment shows how a variety of new organic forms may quickly be produced by cross-breeding, leading to the combination in one race of characters previously found separately in different races. Thus, in