—“{_s - a ae ors Mees Se 
ADDRESS. Ixxxv 
could the offspring of the same progenitor so far deviate from each other as to 
constitute different species. The function of the experimental philosopher is 
to combine the conditions of nature and to produce her results; and this 
was the method of Darwin*. He made himself acquainted with what could, 
without any manner of doubt, be done in the way of producing variation. 
He associated himself with pigeon-fanciers—bought, begged, kept, and 
observed every breed that he could obtain. Though derived from a 
common stock, the diversities of these pigeons were such that “a 
score of them might be chosen which, if shown to an ornithologist, 
and he were told that they were wild birds, would certainly be ranked 
by him as well-defined species.” The simple principle which guides 
the pigeon-fancier, as it does the cattle-breeder, is the selection of some 
variety that strikes his fancy, and the propagation of this variety by 
inheritance. With his eye still directed to the particular appearance 
which he wishes to exaggerate, he selects it as it reappears in succes- 
sive broods, and thus adds increment to increment until an astonish- 
ing amount of divergence from the parent type is effected. The breeder 
in this case does not produce the ¢clements of the variation. He simply 
observes them, and by selection adds them together until the required 
result has been obtained. ‘No man,” says Mr. Darwin, “ would ever 
try to make a fantail till he saw a pigeon with a tail developed in some 
slight degree in an unusual manner, or a pouter until he saw a pigeon 
with a crop of unusual size.” Thus nature gives the hint, man acts 
upon it, and by the law of inheritance exaggerates the deviation. 
Having thus satisfied himself by indubitable facts that the organi- 
zation of an animal or of a plant (for precisely the same treatment applies to 
plants) is to seme extent plastic, he passes from variation under domesti- 
cation to variation under nature. Hitherto we have dealt with the adding 
together of small changes by the conscious selection of man. Can Nature 
thus select? Mr. Darwin’s answer is, “ Assuredly she can.” ‘The number 
of living things produced is far in excess of the number that can be sup- 
ported ; hence at some period or other of their lives there must be a struggle 
for existence; and what is the infallible result? If one organism were 
a perfect copy of the other in regard to strength, skill, and agility, external 
conditions would decide. But this is not the case. Here we have the 
fact of variety offering itself to nature, as in the former instance it offered 
itself to man; and those varieties which are least competent to cope with 
surrounding conditions will infallibly give way to those that are most com- 
petent. To use a familiar proverb, the weakest comes to the wall. But the 
triumphaut fraction again breeds to overproduction, transmitting the qualities 
which secured its maintenance, but transmitting them in different degrees. 
The struggle for food again supervenes, and those to whom the favourable 
quality has been transmitted in excess will assuredly triumph. It is 
easy to see that we have here the addition of increments favourable to 
the individual still more rigorously carried out than in the case of 
domestication; for not only are unfavourable specimens not selected by 
nature, but they are destroyed. This is what Mr. Darwin calls “ Natural 
Selection,” which “acts by the preservation and accumulation of small 
inherited modifications, each profitable to the preserved being.” With this 
idea he interpenetrates and leavens the vast store of facts that he and others 
* The first step only towards experimental demonstration has been taken. Experi- 
ments now begun might, a couple of centuries hence, furnish data of incalculable valve, 
which ought to be supplied to the science of the future, 
