EVOLUTION AS SHOWN BY THE DEVELOPMENT OF THE INDIVIDUAL ORGANISM
By Ernest William MacBride
Professor of Zoölogy, Imperial College of Science and Technology, London; Vice President of the Zoölogical Society of London
According to the theory of evolution as it is applied to zoölogy the fundamental likenesses or homologies among animals are the expressions of blood relationship. We believe, for example, that all the various species which belong to the cat tribe—such as the domestic cat, the leopard, the jaguar, the puma, the lynx, the lion, and the tiger—are the descendants of a primeval species of cat, just as the dog, the fox, the jackal, and the wolf are the descendants of a primeval species of dog. Furthermore, we believe that the primeval dog and the primeval cat were distant cousins, and that millions of years ago both were represented by one species of primitive carnivore, from which both have been derived.
Now the human body resembles the body of a higher ape just as the body of the cat resembles that of the dog; and if our ideas as to the relationship between cats and dogs are sound it must follow that apes and men have been gradually developed out of one and the same ancestral species. But we assume that evolution proceeds very slowly—that great changes require millions of years—so that direct evidence of it is impossible to obtain. To get such evidence, indeed, we
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