This used to be considered a fixed law of nature, constituting
the absolute test and criterion of a _species_ as distinct from a
_variety_; and so long as it was believed that species were separate
creations, or at all events had an origin quite distinct from that of
varieties, this law could have no exceptions, because, if any two
species had been found to be fertile when crossed and their hybrid
offspring to be also fertile, this fact would have been held to prove
them to be not _species_ but _varieties_. On the other hand, if two
varieties had been found to be infertile, or their mongrel offspring to
be sterile, then it would have been said: These are not varieties but
true species. Thus the old theory led to inevitable reasoning in a
circle; and what might be only a rather common fact was elevated into a
law which had no exceptions.
The elaborate and careful examination of the whole subject by Mr.
Darwin, who has brought together a vast mass of evidence from the
experience of agriculturists and horticulturists, as well as from
scientific experimenters, has demonstrated that there is no such fixed
law in nature as was formerly supposed.
Pages:
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290