398 LAMARCK, HIS LIFE AND WORK 



" Neolamarckism gathers up and makes use of 

 the factors both of the St. Hilaire and Lamarckian 

 schools, as containing the more fundamental causes 

 of variation, and adds those of geographical isolation 

 or segregation (Wagner and Gulick), the effects of 

 gravity, the effects of currents of air and of water, 

 of fixed or sedentary as opposed to active modes of 

 life, the results of strains and impacts (Ryder, Cope, 

 and Osborn), the principle of change of function as 

 inducing the formation of new structures (Dohrn), 

 the effects of parasitism, commensalism, and of sym- 

 biosis — in short, the biological environment ; together 

 with geological extinction, natural and sexual selec- 

 tion, and hybridity. 



" It is to be observed that the Neolamarckian in 

 relying mainly on these factors does not overlook 

 the value of natural selection as a guiding principle, 

 and which began to act as soon as the world became 

 stocked with the initial forms of life, but he simply 

 seeks to assign this principle to its proper position 

 in the hierarchy of factors. 



" Natural selection, as the writer from the first 

 has insisted, is not a vera causa, an initial or impel- 

 ling cause in the origination of new species and gen- 

 era. It does not start the ball in motion; it only, 

 so to speak, guides its movements down this or that 

 incline. It is the expression, like that of " the sur- 

 vival of the fittest" of Herbert Spencer, of the re- 

 sults of the combined operation of the more funda- 

 mental factors. In certain cases we cannot see any 

 room for its action; in some others we cannot at 

 present explain the origin of species in any other 

 way. Its action increased in proportion as the world 

 became more and more crowded with diverse forms, 

 and when the struggle for existence had become 

 more unceasing and intense. It certainly cannot 

 account for the origination of the different branches, 

 classes, or orders of organized beings. It in the 



