A
study of Darwin's book, and a general glance at the present state of
the natural sciences, enable us to gather the following as perhaps
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;--the patent fact, 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, perhaps 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 appear to vary
little, others moderately, others immoderately, to the great
bewilderment of systematic botanists and zoologists, and their
increasing disagreement as to whether various forms shall be held to
be original species or marked varieties.
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