We may at once proceed to the retrogressive or negative varieties. The
arguments for the assumption that elementary species owe their origin to
the acquisition of new qualities may well be left for later lectures
when we shall deal with the experimental proofs in this matter.
There are three larger groups of facts, on which the assumption of
latent characters in ordinary varieties rests. These are true atavism,
incomplete loss of characters, and systematic affinity. Before dealing
with each of these separately, it may be as well to recall once more
that in former lectures we have treated the apparent losses only as
modifications in a negative way, without contemplating the underlying
causes.
Let us recall the cases of bud-atavism given by the whitish variety of
the scarlet _Ribes_, by peaches and nectarines, and by conifers,
including _Cephalotaxus_ and _Cryptomeria_. These and many other
analogous facts go to prove the relation of the variety to the species.
Two assumptions are allowable. In one the variety differs from the
species by the total loss of the [227] distinctive character. In the
other this character is simply reduced to an inactive or dormant state.
The fact of its recurrence from time to time, accompanied by secondary
characters previously exhibited, is a manifest proof of the existence of
some relation between the lost and the resumed peculiarity.
Pages:
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231