170 BOTANICAL GAZETTE [march 



by slow and almost invisible changes as was assumed by Darwin. 

 The theory itself does not, of course, depend on this or other single 

 instances; it is founded upon general considerations taken from 

 almost all branches of biological and paleontological research, as 

 I have often pointed out/ 



One of the main arguments is the statement that adaptations 

 cannot, as a rule, have been produced by slow improvements, and 

 that quite a large number of differentiations in organization, if not 

 almost all the really important ones among them, are not adapta- 

 tions at all. 



Apart from our poetical admiration of nature, we have no other 

 way of judging the reality and efficiency of supposed adaptations 

 than by their effects in the struggle for life. Species which are 

 distributed over large countries and occur in thousands of indi- 

 viduals are evidently well fitted for their life conditions. Newly 

 introduced forms, which are spreading with astonishing rapidity 

 and gaining a large territory often in the lapse of a few years, 

 thereby show the highest degree of adaptation to their new environ- 

 ment. But a showy differentiation may be followed by a wide 

 distribution, as in the case of Drosera, or limit the species to a 

 relatively very small area, as in Dionaea. 



Of late J. C. Willis has brought forward the most conclusive 

 evidence against the theory of natural selection and in favor of an 

 origin of species by mutation.'' He bases some of his arguments 

 upon his observations of the endemic species of Ceylon, such as are 

 found in Coleus, Acrotrema, and other genera. If these endemics 

 had evolved according to the law of natural selection, in consequence 

 of a gradually increasing adaptation to their local environment, 

 it would follow that they must now be better adapted than their 

 parent types, conquer these in the struggle for life, and become 

 quite common, while the old forms would tend to disappear. As 

 a matter of fact, however, their behavior is quite the contrary. 



" DeVeies, Hugo, The mutation theory. 2 vols, igog-igio; Species and varieties, 

 their origin by mutation, 2d ed., 1906; Die Mutationen in der Erblichkeitslehre. pp. 42. 

 Berhn. 1912; The principles of the theory of mutation. Science 40: 77-84. 1914. 



' Willis, J. C, Some evidence against the theory of the origin of species by natural 

 selection of infinitesimal variations, and in favor of origin by mutation. Ann. Roy. 

 Bot. Gard. Peradeniya 4:1-15. 1907. 



