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, Itis*the expression; likesthat 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 
