456 THE POPULAR SCIENCE MONTHLY 



been continuously increased, this being the great motive power of the 

 strenuous activity exhibited by these charming little creatures. 



Lord Salisbury on Natural Selection 



As illustrating the strange and almost incredible misconceptions 

 prevailing as to the mode of action of natural selection, the lecturer 

 quoted the following passage from the late Lord Salisbury's presiden- 

 tial address to the British Association at Oxford in 1894. After de- 

 scribing how the diverse races of domestic animals have been produced 

 by artificial selection, Lord Salisbury continued thus : 



But in natural selection, who is to supply the breeder's place? Unless the 

 crossing is properly arranged the new breed will never come into being. What 

 is to secure that the two individuals of opposite sexes in the primeval forest, 

 who have been both accidentally blessed with the same advantageous variation, 

 shall meet, and transmit by inheritance that variation to their successors? 

 Unless this step is made good the modification will never get a start; and yet 

 there is nothing to ensure that step but pure chance. The law of chance takes 

 the place of the cattle-breeder or the pigeon-fancier. The biologists do well to 

 ask for an immeasurable expanse of time, if the occasional meetings of advan- 

 tageously varied couples, from age to age, are to provide the pedigree of modi- 

 fications which unite us to our ancestors, the jelly-fish. 



Here we have the extraordinary misconception presented to a 

 scientific audience as actual fact, that advantageous variations occur 

 singly, at long intervals, and remote from each other; each statement 

 being, as is well known, the absolute reverse of what is really the case. 

 It totally ignores the fact, that every abundant species consists of tens 

 or hundreds of millions of individuals, and that as regards any faculty 

 or quality whatever, this vast host may be divided into two portions 

 — the less and the more adapted — not very unequal in amount. It 

 follows that at any given time, in any given country, the advantageous 

 variations always present are not to be counted by ones and twos, as 

 stated by Lord Salisbury, but by scores of millions; and not in indi- 

 viduals widely apart from each other, but constituting in every locality 

 or country, somewhere about one half of the whole population of the 

 species. 



The facts of nature being what they are, it is impossible to imagine 

 any slow change of environment to which the more populous species 

 would not become automatically adjusted under the laws of multipli- 

 cation, variation and survival of the fittest. Almost every objection 

 that has been made to Darwinism assumes conditions of nature very 

 unlike those which actually exist, and which must, under the same 

 general laws of life, always have existed. 



Protective Color and Mimicry 

 The phenomena of protective coloration and mimicry were very 

 briefly alluded to, both because they are comparatively well known and 



