Darwin made easy / by Edward B. Aveling.

  • Edward Aveling
Date:
1893
Catalogue details

Licence: Public Domain Mark

Credit: Darwin made easy / by Edward B. Aveling. Source: Wellcome Collection.

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    The great cause of the sterility between animals and plants sufficiently different one from another to be placed in different species, is probably difference in their sexual elements, a difference not the result of interposition from without, but of the modification these elements have under- gone as the living beings in which they are produced have been exposed to different external conditions. In this discussion Darwin makes a fair use of analogy* He points out that certain trees can be grafted one upon another, whilst others are incapable of being thus grafted. Thus, the pear can be grafted upon the quince, and, with greater difficulty, upon the apple, a plant, by the way, more nearly allied to the pear than is the quince. But the pear cannot be grafted upon an elm. This difficulty of grafting is not referred to any special creative act. Indeed, the distinctions between plants that would be founded on the ease or difficulty of grafting would not coincide at all with the classification-divisions, and distinctions at present recognised—i.e., if we based our species on the possibility or impossibility of grafting, the species thus mapped out would not be identical with those recognised to-day. Yet generally it may be said that plants closely allied can thus be blended, and that if they are not closely allied, grafting js impossible. As Darwin puts it: “ There is no more reason to think that species have been specially endowed with various degrees of sterility to prevent their crossing and blending in nature, than to think that trees have been specially endowed with various and somewhat analogous degrees of difficulty in being grafted together in order to prevent their inarching in our forests.” Again, to take an illustration from the highest living thing, certain races of man cannot interbreed. Thus the Egyptian women and the whites are almost universally infertile. If the believer in special creation holds that species, as originally created, were doomed to infertility one with another, he must at least believe that more than one species of man were cheated, and that the Adam and Eve story is open to suspicion. When we consider that the amount of sterility between individuals of the same species varies, that with changed conditions the sterility of individuals is affected, that the study of the anatomy and physiology of plants and animals
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