2 THE COEFFICIENT OF MUTATION IN OENOTHERA BIENNIS L. 



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. 1 ) 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. 

 The endemics are rare, often strictly local, and grow in the midst 

 of a luxuriant vegetation of their widely spread and thriving 

 ancestors. It is hardly necessary to point out that this conclusion 

 holds good not only for Ceylon, but for the origin of endemic and 

 local species in general. 



Willis has also called attention to the Podostemaceae and the 

 allied group Tristichaceae. They show one of the most interesting 

 illustrations of a very rich differentiation without the least in- 

 dication of a relation to their environment. A very great uni- 

 formity in the conditions of life is combined with a most remarkable 

 variety in their morphological structure. In the Podostemaceae 

 die flowers are anemophilous, terminal, and erect, but combine 

 with these characters of low organization the highest degrees of 



i) 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. 



