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 
BaLpwin, J. M. A New Factor in Evolution. Amer. Natural, XXX. 
1896. 
Banesen. W. Presidential Address. Report of the 74th Meeting of the 
British Assoc. (1904). 1905. 
Burron, G. L. Historie Naturelle. 1755. 
Crampton, H. E. On a General Theory of Adaptation and Selection. 
Jour. of Exper. Zool. II. 1905. 
DarRBESHIRE, 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. Zoédnomia. 1794. 
The Botanic Garden. 1788. 
Duccescat, V. Les Problémes biochimiques dans la Doctrine de l’Evo- 
lution. Arch. ital. de Biol. XLIIT. 1905. 
