Page:Evolution of Life (Henry Cadwalader Chapman, 1873).djvu/195

Rh caused by the greater number in Paraguay of a certain fly which lays its eggs in the navels of these animals when first born," the new-born dying in consequence of these inroads. As illustrating the struggle for existence, Prof. Haeckel calls attention to the effect of placing goats or pigs on one of the isolated oceanic islands uninhabited by man. These animals ran wild, and meeting no enemies, and finding at first plenty of food, increased in such surprising numbers that they killed the other animals and plants. Thus, in the course of time, the whole island was nearly depopulated, the goats or pigs even dying out for want of food. In some cases dogs were let loose, after the island hud been overrun by goats or pigs. The dogs, finding an abundance of food at first, increased so rapidly that their very numbers made food so scarce that they finally died out.

Many other interesting examples of the struggle for existence might be mentioned; those just noticed suffice, however, to call attention to the important relation existing, in this respect, between plants and animals. We turn now to a consideration of the facts of Inheritance and Variation.

Not only does the offspring resemble the parent in the manner of its growth, in the form of its body and general appearance, but, as is well known, mental peculiarities are also inherited, the development of particular talents for music, painting, etc. being conspicuous in certain families: thus, the Bach family have numbered twenty distinguished musicians, the family of Weber upwards of forty. Less pleasant peculiarities, as those of diseases of all kinds, are well known to reappear in posterity both at the same time and in the same place as they first appeared in the parent. In a word, generally speaking, "Like begets like." This