ARTICLES 399 



of the progeny of short individuals was actually longer than the 

 carapace length of the offspring of long individuals. But in 

 any group of water-fleas selected at random there are several 

 different strains which tend to give rise to groups of individuals 

 with different standards of carapace length ; and if we select 

 from such a population all those with longer carapace for further 

 breeding, we do get a population with a longer average length 

 of carapace, owing to the elimination of all those strains with 

 short standards of carapace length. It was this circumstance 

 that gave to Darwin the illusion that it was possible by selection 

 alone to increase or diminish the size of an organ indefinitely ; 

 but when once the population has been purified by the elimina- 

 tion of all strains with different standards from that aimed at, 

 progress comes to an abrupt end. 



An exactly similar result has been arrived at by Jennings, 

 who studied the reproduction of the Protist Paramecium (the 

 Slipper Animalcule), and by Johannsen, who studied the weight 

 of beans produced by the scarlet runner. If we consider how 

 far apart in the organic scale a flowering plant, a Crustacean, 

 and a Protist are, and how concordant are the results arrived 

 at, we shall gain a strong conviction that selection alone, when 

 the environment remains constant, is powerless to effect evolution. 

 If once this conclusion be granted, the whole supposed 

 advantage of Darwin's theory over Lamarck's disappears ; the 

 pathological mutants which Mendelians employ for their 

 experiments are utterly unlike the variations which the study 

 of comparative anatomy induces us to postulate as the material 

 of evolution, and we seem to be driven back on Lamarck's 

 view of the inheritability of the effects of use and disuse as the 

 only alternative. 



This feeling is shared by a large number of palaeontologists. 

 In the early days of this science, no exact series of related forms 

 had been discovered, but more recently whole successions of 

 closely related forms preserved in strata, following each other 

 directly in time, have come to light. No reasonable person 

 doubts that in these successions we have the actual records 

 of evolution before us. If we now study the changes which take 

 place in these series, they bear no relation to the ''mutations " 

 found as sports in gardens and by cattle-breeders, but they 

 do closely resemble those enlargements and diminutions of 

 organs which Lamarck stated would result from the effects of 

 use and disuse, and they can be shown to occur independently 

 in animals of quite distinct ancestry. 



We can trace the ancestral horse from a stage in which he 

 had tapir-like feet, and evidently frequented swampy ground, 

 step by step until, by the gradual shrinking of the superfluous 

 toes, he was transformed into the one-toed animal we are 



