174 NATURAL SCIENCE [September 
countenance to Darwin’s idea, that a species must have a numerous 
population to produce varieties, the rule seems rather to be that 
these two features do not necessarily coincide at all. 
Supposed Aids to Natural Selection.—In order to secure 
the survival of the fittest, 72, a new variety among the parent form, 
it was perceived that two additional and hypothetical aids were 
necessary, viz., (1) some degree of infertility with the parent, and 
(2) a rapidity of adaptation. 
With regard to the first, all experience goes to prove that it 
does not exist; for when cultivators wish to fix a new race, as of 
cabbage, &c., they are obliged to grow it as far as possible away 
from the parent stock. Indeed, considering how freely species can 
be hybridised, the probability of an offspring refusing to be crossed 
by the same species is very small or nil. Neither Darwin nor Dr 
Wallace bring forward any examples of infertility with the parent 
among plants. 
Secondly, a rapidity of adaptation is claimed hypothetically. 
This does often really exist, but it is a little uncertain whether 
these authors were aware of it. For when a plant finds itself in a 
new and markedly different environment, which strongly affects it, 
it then grows by self-adaptation in response to the new external 
influences : as when passing from water to land, or vice versé; from 
the wild state to the artificial soil of a garden; from lowlands to 
alpine or subarctic localities, &c.,as I have shown in “ The Origin of 
Plant Structures.” 
The Persistence or non-retention of new varietal 
characters.—To come to what Dr Wallace regarded as the 
most important point in his paper. Four times does he mention 
it, only slightly altering the expression, e.g., he says:—“ No attempt 
has been made to show, even hypothetically, how, through the 
action of known causes, such characters [useless ones], when they 
do arise, can become first extended to every individual of a species, 
and then be totally obliterated as regards any portion of the species 
which may become modified so as to constitute a new species. 
Useful characters thus strictly limited are the necessary and 
logical results of modification through survival of the fittest. No 
agency has been shown to exist capable of producing useless 
characters similarly limited.” As illustrations to meet Dr Wal- 
lace’s demand, it may be observed that the races of cultivated 
pears are spineless; yet they are derived from the wild Pyrus 
communis, which has useless abortive branches as spines. Similarly 
is it the case with some varieties of plums derived from Prunus 
communis. 
With regard to the retention of injurious characters, the 
1 Loc. cit., p. 491. 
