In Yorkshire, it is historically known that
the ancient black cattle were displaced by the long-horns, and that these
"were swept away by the short-horns" (I quote the words of an agricultural
writer) "as if by some murderous pestilence."
DIVERGENCE OF CHARACTER.
The principle, which I have designated by this term, is of high importance,
and explains, as I believe, several important facts. In the first place,
varieties, even strongly-marked ones, though having somewhat of the
character of species--as is shown by the hopeless doubts in many cases how
to rank them--yet certainly differ far less from each other than do good
and distinct species. Nevertheless according to my view, varieties are
species in the process of formation, or are, as I have called them,
incipient species. How, then, does the lesser difference between varieties
become augmented into the greater difference between species? That this
does habitually happen, we must infer from most of the innumerable species
throughout nature presenting well-marked differences; whereas varieties,
the supposed prototypes and parents of future well-marked species, present
slight and ill-defined differences. Mere chance, as we may call it, might
cause one variety to differ in some character from its parents, and the
offspring of this variety again to differ from its parent in the very same
character and in a greater degree; but this alone would never account for
so habitual and large a degree of difference as that between the species of
the same genus.
Pages:
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190