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 Physiology 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, " in the 



* " The Origin of Species without the Aid of Natural Selection," 

 Natural Science, Oct., 1894. Also, " The Origin of Plant Structures. " 



