226 The Science of Life. 



tending more and more to emphasize the all-sufficiency 

 of natural selection operating upon spontaneous varia- 

 tions. To the main doctrine Darwin himself added his 

 subsidiary theory of Sexual Selection, a particular case 

 of Natural Selection, which his colleague Wallace re- 

 fused to accept. To the latter, however, it seemed 

 necessary to confess the inadequacy of Natural Selec- 

 tion to explain the higher qualities of man, and he 

 postulated waves of spiritual influx to help the material 

 world over this and other obstacles in its course, a 

 position which, to Spencer for instance, seemed an 

 unwarranted loss of faith in science. But Spencer again 

 was no strict Darwinian, remaining, like Haeckel and 

 others, a firm believer in Lamarckism. Most impor- 

 tant, however, was an addition to the Selection theory, 

 suggested by several naturalists, such as Wagner, but 

 brought into prominence by Romanes and Gulick, the 

 theory of "Isolation", without which the divergence of 

 species from a common stock is inexplicable. Isolation 

 is a general term for various processes which tend to 

 restrict the range of intercrossing with a species, and to 

 bring similar variants to pair together. 



Another position is that of the Lamarckians and 

 Buffonians, who emphasize the transforming power of 

 function (use and disuse) and of changed environment 

 (all manner of surrounding influences), and believe in 

 the transmission of acquired characters or modifica- 

 tions. They are sometimes, though not elegantly, 

 called " transmissionists ". The school has found its 

 chief supporters in France, where Lamarck in his life- 

 time got such scant justice, and in America, where it 

 seems to be in the ascendant. It must be noted that 

 not a few, e.g. Haeckel and Spencer, combine a belief 

 in modification-inheritance with a selectionist position. 



The doctrine of the Lamarckian and BufFonian school 

 owes its strength to the fact that an individual organism 

 is certainly influenced by what it does or does not do, 

 and is plastic in the grip of its surroundings ; its weak- 

 ness is in the absence of evidence to show that the 

 modifications or bodily changes so acquired are in any 

 degree transmissible from parents to offspring. It was 



