Vol. XXXV.] 



128 



Obs. Before naming this bird I have examined all 

 the members o£ this group in the British and Tring 

 Museums. The characters of this subspecies are found to 

 be constant. 



The remainder of the evening was devoted to a Discus- 

 sion on 



" The Effect of Environment on the Evolution of Species.^' 



The Chairman * : It is much less easy, at the present day, 

 to discuss Environment and its influence on Evolution than 

 it was a few years ago, owing to the experiments carried 

 out in connection with the study of the " Meudelian Law.'* 

 This study and the experiments connected with it have 

 led many biologists to the conviction that all variation is 

 fortuitous, and that the fixity of certain types and the con- 

 tinuance of evolution are entirely due to the action of the 

 Mendelian Law. It would take much longer than the time 

 at my disposal to discuss adequately these experiments, or to 

 explain why the exponents of " Mendelism " have, in many 

 instances, come to the conclusions which they expound. 

 In this discussion I propose to follow the lines of reason- 

 ing which have led to my personal conclusions, and to leave 

 it to others to prove or disprove these conclusions as well as 

 they are able. It is my opinion that climatic and other local 

 conditions start the variation, and that the Darwinian law 

 of the survival of the fittest directs and maintains this varia- 

 tion, but that the Mendelian law, by hastening the process 

 of evolution in the direction in which it began, finally com- 

 pletes the process. Many obstacles appear in the path 

 of the student, for it is, at this late stage in biological 

 evolution, often impossible to trace the lines on which it 

 has taken place, and therefore very difficult to determine 

 which factors in environment have acted in a given case. 



* A list of the specimens exhibited by Lord Rothschild to illustrate 

 his address is given on pp. 140-142. 



