Page:The Zoologist, 4th series, vol 2 (1898).djvu/419

Rh as a law acting through space and time; so that we narcotise our mind with a new dogma: not that in the beginning was the "word," but "natural selection."

This endeavour to make natural selection the all and all of evolution has in some cases brought about a reaction which denies its efficacy in toto. Thus the Rev. G. Henslow, in a recent interesting work, ascribes the origin of species "to the joint action alone of two great factors of evolution—variability and environment." Mr. Henslow does good service in recording a large number of facts and observations, which go to prove to demonstration that the environment largely induces the form and structure of vegetable life, and he formulates the proposition that these features are due "to the responsive power of protoplasm, which, under the influences of the external forces of the environment, builds up just those tissues which are the best fitted to be in harmony with the environment in question." But, alas! La phrase est le tyran de notre siecle. The term "responsive power of protoplasm" is, like that of "germ plasm," workable, but unprovable. It refers to a fact, and seeks to explain it by a suggestion. But even if we accept this "responsiveness of protoplasm to the environmental conditions," natural selection is not banished, but only limited. It is still a cause, but not an absolute one; it has had an elementary and preserving process in a stage of life it did not create. Thus, if spinescent characters in plant-life seem undoubtedly due to drought, and usually possess an arid environment, as one may read who ever gazes on the Transvaalian veld, plants still survive, and could only have survived the effects of the foraging powers of the immense herds of ruminants which formerly swarmed over the land, by the possession of spines of defence, Although these animals are