A study of Darwins
book, and a general glance at the present state of the natural
sciences, enable us to gather the following as among the most
suggestive and influential. We can only enumerate them here, without
much indication of their particular bearing. There is--
1. The general fact of variability, and the general tendency of the
variety to propagate its like--the patent facts that all species vary
more or less; that domesticated plants and animals, being in conditions
favorable to the production and preservation of varieties, are apt to
vary widely; and that, by interbreeding, any variety may be fixed into
a race, that is, into a variety which comes true from seed. Many such
races, it is allowed, differ from each other in structure and
appearance as widely as do many admitted species; and it is practically
very difficult, even impossible, to draw a clear line between races and
species. Witness the human races, for instance. Wild species also
vary, perhaps about as widely as those of domestication, though in
different ways. Some of them apparently vary little, others moderately,
others immoderately, to the great bewilderment of systematic botanists
and zoologists, and increasing disagreement as to whether various forms
shall be held to be original species or strong varieties.
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