Nos. 622-623] MIGRATION A FACTOR IN EVOLUTION 467 



and furthermore, not having seen this formulated and 

 applied to evolution as here presented, I feel that the im- 

 portance of the subject merits this treatment. 



Special attention is called to the fact that this discus- 

 sion is not intended as a complete, scientific explanation 

 of migrational facts, but as the presentation of a point 

 of view, or working hypothesis, which it is believed will 

 aid in explaining many well-known facts and relations, 

 and will aid in the discovery of new ones. An effort has- 

 been made to frame this hypothesis in such a manner as 

 not to prejudice the problems investigated, or to inter- 

 fere seriously with the various constructive schools of 

 investigation, although I am well aware that this hy- 

 pothesis, like all others, is built upon certain assumptions. 



During the preparation of this paper (which amplifies 

 certain ideas which I have previously outlined) I was 

 much impressed by finding so much eonlirniatory evi- 

 dence of the general validity of the dynamic stain loo int. 

 in fields relatively remote from migration. The inde- 

 pendent growth of such conceptions in diverse fields is 

 indicative that many subjects are independently reaching 

 a certain common stage of development and that spon- 

 taneously such ideas are becoming independent organiz- 

 ing centers of activity. By interaction and regulation 

 among these ideas, new higher systems of unity and cor- 

 relation are developing, which are producing important 

 effects in zoology as well as in other sciences. The slow- 

 ness seen in the application of dynamic ideas to biology 

 is perhaps rather natural as is evident when we recall the 

 fact that even in the simpler physical sciences we have 

 as yet no complete dynamical theory or system, although 

 much progress has been made, not, however, toward a 

 complete system, but toward that dynamic equilibrium 

 which characterizes a growing subject. 



II. The Process Method of Animal Responses 

 1. Introduction 

 The fundamental assumption upon which this discus- 

 sion is founded is that the animal should be looked upon 



