Page:Popular Science Monthly Volume 42.djvu/774

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plants, or I might shortly say, of all living creatures to one another. It used to be assumed that the highest plants and highest animals were to be compared together, but all attempts to make this comparison rationally were unsuccessful; and it was only when an old member of this society, Mr. Charles Darwin, pointed out that animals and plants had sprung from one common ancestor and had diverged in different directions that the various relationships became intelligible. I well remember that when learning botany it puzzled me greatly to understand why the shape of the ovary, the nature of the ovule, and the position of the embryo should be such important characters in determining the genus of plants, and I devoutly wished that plants had been made in such a way that one could settle their nature by characters visible to the naked eye and not requiring a pocket microscope.

PSM V42 D774 Four different species of embryos.jpg
Fig. 1.—Chick. Fig. 2.—Tortoise. Fig. 3.—Hog. Fig. 4.—Man.
(After Haeckel.)

But the reason for all this at once became evident when the Darwinian doctrine showed that it is in these embryonic characters that relationships are to be discovered and that it is in later development that differences occur. As Haeckel has shown, the embryos of the fowl, the tortoise, the hog, and the man, are all nearly alike in the early stages of feetal life (Figs. 1, 2, 3, and 4), utterly different as these creatures may be when they have attained their full development—the Darwinian doctrine has thrown a flood of light on the relationship of plants and animals, and shows us that when animals have got as it were on the wrong track, however far they may go in it, they never come to anything very good.

Nobody expects much of a jellyfish. Its soft, pulpy substance is incapable of anything but the simplest movement, and no animal that has not something hard to steady it can greatly excel the jellyfish. The soft mollusks which use their hard casing only for protective purposes, like the oyster and the snail, are bound to stay low in the scale of existence, and the highest mollusk (the octopus) appears to be striving after something better, but only