414 LAMARCK, HIS LIFE AND WORK 
is popularly supposed, on direct proof, but is ad- 
duced as an hypothesis which gains its strength from 
being compatible with so many facts of correlation 
between an organism and its surroundings. Yet the 
same writer who considers natural selection proved 
will call for positive experimental proof of Lamarck’s 
theory, and refuse to accept its general compatibility 
with the facts as support. Almost any case where 
natural selection is held to act by virtue of advan- 
tage gained by use of a part is equally compatible 
with Lamarck’s theory of use and development. 
The wings of birds of great power of flight, the rela- 
tions of insects to flowers, the claws of beasts of 
prey, are all cases in point.”’ 
Professor J. A. Thomson’s useful Synthetic Sum- 
mary of the Influence of the Environment upon the 
Organism (1887) takes for its text Spencer’s apho- 
rism, that the direct action of the medium was the 
primordial factor of organic evolution. Professor 
Geddes relies on the changes in the soil and climate 
to account for the origin of spines in plants. 
The botanist Sachs, in his Physzology of Plants 
(1887), remarks: ‘‘ A far greater portion of the phe- 
nomena of life are [is] called forth by external influ- 
ences than one formerly ventured to assume.”’ 
Certain botanists are now strong in the belief that 
the species of plants have originated through the 
direct influence of the environment. Of these the 
most outspoken is the Rev. Professor G. Henslow. 
His view is that self-adaptation, by response to the 
definite action of changed conditions of life, is the 
true origin of species. In 1894* he insisted, ‘* 2 the 
* “ The Origin of Species without the Aid of Natural Selection,” 
Natural Science, Oct., 1894. Also, ‘* The Origin of Plant Structures.” 
