Preface 



which the Darwinian theory seems to require 

 modification. 



This volume originated as the result of several 

 conversations we, the joint authors, had last 

 summer. We discovered that we had a great 

 many ideas in common on the subject of evolution. 

 This seemed strange, seeing that our education 

 had not been on the same lines. One of us took 

 a degree in natural science at Cambridge, and 

 subsequently entered His Majesty's Indian Civil 

 Service, but continued his zoological studies in 

 India as a hobby. The other, a naturalist from 

 childhood, nevertheless took a classical degree at 

 Oxford, then received a technical zoological train- 

 ing, adopted zoology as a profession, and held 

 for some years a position in the Natural History 

 Museum at Calcutta. 



Our conversations revealed that we were both 

 of opinion that biology is in an unhealthy con- 

 dition, especially in England, and that the science 

 sorely needs some fresh impetus. Neither of us 

 had the time to attempt, single-handed, to give 

 the required impetus, but as one of us happened 

 to be home on eighteen months' leave, we thought 

 we might undertake the task in collaboration. 



We felt that we might collaborate the more 

 successfully because the large number of facts 

 collected by the one of us form the necessary com- 

 plement to the philosophical studies of the other. 



We have endeavoured, so far as possible, to 



