THE BELFAST ADDRESS 



that is the impression of the vast amount 

 of labour, both of observation and of 

 thought, implied in its production. Let 

 us glance at its principles. 



It is conceded on all hands that what 

 are called "varieties" are continually 

 produced. The rule is probably with- 

 out exception. No chick, or child, is in 

 all respects and particulars the counter- 

 part of its brother and sister ; and in 

 such differences we have " variety " in- 

 cipient. No naturalist could tell how far 

 this variation could be carried ; but the 

 great mass of them held that never, by 

 any amount of internal or external 

 change, nor by the mixture of both, 

 could the offspring of the same progenitor 

 so far deviate from each other as to con- 

 stitute 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. 1 He made himself 

 acquainted with what could, without 

 any manner of doubt, be done in the 

 way of producing variation. He asso- 

 ciated 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 

 re-appears in successive broods, and thus 

 adds increment to increment until an 

 astonishing amount of divergence from 

 the parent type is effected. The breeder 



1 The first step only towards experimental 

 demonstration has been taken. Experiments 

 now begun might, a couple of centuries hence, 

 furnish data of incalculable value, which ought 

 to be supplied to the science of the future. 



in this case does not produce the elements 

 of the variation. He simply observes 

 them, and by selection adds them together 

 until the required result has been ob- 

 tained. " 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 indu- 

 bitable facts that the organisation of an 

 animal or of a. plant (for precisely the 

 same treatment applies to plants) is to 

 some extent plastic, he passes from varia- 

 tion under domestication 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 

 supported ; 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 con- 

 ditions 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 com- 

 petent to cope with surrounding con- 

 ditions will infallibly give way to those 

 that are most competent. To use a 

 familiar proverb, the weakest goes to the 

 wall. But the triumphant fraction again 

 breeds to over-production, transmitting 

 the qualities which secured its main- 

 tenance, 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 triumph as before. 



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 ; 



