The Theory of Evolution 233 



species; it does not originate them. The same conclusion fol- 

 lows if we suppose that species have been formed by the direct 

 action of the environment, or by progressive stages resulting from 

 internal factors (orthogenesis) ; the survival of the adapted 

 new forms accounts for the general condition of adaptation of 

 living things, but not for the origin of the adaptations, or for 

 the origin of species. The origin of species and the adaptation 

 .of living things may, after all, be different problems. In fact, 

 the question of what constitutes a species has given rise to 

 widely different expressions of opinion, and the entire problem 

 of evolution may have been prejudiced by too much emphasis 

 having been laid on the origin of species. If we admit that 

 species are arbitrary scholastic conventions, their origin is of 

 secondary importance for the theory of evolution compared with 

 the problem of adaptation of living things. It is only from the 

 point of view of classification that the origin of specific differ- 

 ences is of value. If their origin is the same as that of adap- 

 tive differences between individuals, it may be that the conclu- 

 sions derived from the study of specific differences may throw 

 light on the origin of adaptive differences, but if the origin of 

 specific differences is different from the origin of adaptive dif- 

 ferences, the two problems should be studied separately. 



LITERATURE, CHAPTER XIV 



BALDWIN, J. M. A New Factor in Evolution. Amer. Natural, XXX. 

 1896. 



BATESON, W. Presidential Address. Report of the 74th Meeting of the 

 British Assoc. (1904). 1905. 



BUFFON, G. L. Historic Naturelle. 1755. 



CRAMPTON, H. E. On a General Theory of Adaptation and Selection. 

 Jour, of Exper. Zool. II. 1905. 



DARBESHIRE, A. D. On the Difference between Physiological and Statis- 

 tical Laws of Heredity. Mem. and Proc. Manchester Lit. and Phil. 

 Soc. 1905-1906. 



DARWIN, C. The Origin of Species. 1859. 

 The Descent of Man. 



DARWIN, E. Zoonomia. 1794. 

 The Botanic Garden. 1788. 



DUCCESCHI, V. Les Problemes biochimiques dans la Doctrine de 1'Evo- 

 lution. Arch. ital. de Biol. XLIII. 1905. 



