376 Appendix C 



names, to call them 'isolation.' All this seems to the present 

 writer to furnish evidence of the tendency of Romanes, shown 

 also strikingly in his later writing on the inheritance of acquired 

 characters, to lay too much value on logical disquisition. 1 



In thus dwelling on the striking features of physiological 

 selection, as Romanes and Gulick have developed it, I by no 

 means mean to lead the reader to think that this important 

 theory is done justice to ; on the contrary, the book will be 

 found, from many points of view, to build up a claim for this 

 hypothesis as representing a real factor in evolution, especially 

 in divergent evolution,- -which writers who refuse to recognize 

 it, as Mr. Wallace, will have great difficulty in disposing of. 

 And this the more when it is taken in connection with the 

 evidence which Professor Pearson gives to show that ' Repro- 

 ductive Selection ' (on the basis of relative infertility) is actually 

 at work. 



For example, among a certain class in a community, a high 

 relative death-rate among women of narrow hips may serve to 

 establish a correlation between maximum effective fertility (in 

 Pearson's sense) and broad hips ; while in another class in the 

 same community the same maximum fertility may perhaps be 

 established by intentional regulation of size of family with better 

 medical attendance, without any reference to size of hips at all. 

 Here there would be a tendency to divergent evolution in the 

 matter of hip conformation, due simply to ' isolation ' by a social 

 barrier. Romanes' hypothesis calls for the same result where 

 the barrier is the physical one of some degree of gross infertility 

 between the .two groups. I put forward this social instance 

 because, among other reasons, while it is one of the few forms 



1 As to the minor utility of showing that there is such a wider though negative 

 category under which certain of these natural processes may be viewed that, 

 no one, I suppose, would dispute ; but when it comes to considering it a great 

 discovery, and requiring biologists to adopt a new terminology with a view to 

 recognizing it, it would seem to be going too far. Nor does this suggest any 

 disparagement of the fresh and new considerations advanced, especially, in Mr. 

 Gulick's very notable papers. A similar classification of certain of the special 

 ' factors ' under the general head of ' isolation ' is made by F. W. Hutton in 

 Natural Science, October, 1897. 



