Introdudtioru 



In such an investigation as the following the writer is forcibly im- 

 pressed with the soundness of that tenet expressed by Jennings (1924) 

 when he said that "under the same conditions objects of different ma- 

 terial behave diversely; under diverse conditions objects of the same 

 material behave diversely", and that "neither the material constitution 

 alone, nor the conditions alone, will account for any event whatever; 

 it is always the combination that has to be considered". 



In considering such a phenomenally specialized organism as the 

 whale and studying it part by part one is also forcibly impressed by the 

 staggering length of time that it must have taken to produce such a 

 creature, and the intricacy of the evolutional processes that have shaped 

 countless anatomical details to effect proper interaction and interrelation- 

 ship of parts to a single harmonious end. 



The evidences of evolution are most abundant upon every hand, and 

 still we know so very little about them. Tentative theories are advanced 

 and discussed, but the ways of evolution are so exceedingly deliberate 

 that the lifetime of a single investigator is not sufficiently long for him 

 to observe its natural processes. O. P. Hay (1928) has stated "A learned 

 writer on mammals tells me he doubts that a single new species has de- 

 veloped since the first interglacial stage", which was "perhaps 400,000 

 years" ago. If this be the case I do not see how the whales have evolved 

 from a terrestrial ancestor in less than one hundred million years, and 

 two hundred million might be all too short. How, then, can we expect 

 successfully to investigate the processes of evolution in the laboratory.^ 

 This element of vast time should be stressed, and also, although we 

 know little about the ways of evolution, we cannot help formulating 

 tentative hypotheses of explanation. 



The writer is strongly convinced that we cannot look to any one 

 theory to explain evolution. The whale is very different indeed from 

 the generalized type of mammal in a great many major details, and hun- 

 dreds and even thousands of minor details, involving billions of cells. 

 These items have been changed doubtless by numberless evolutional 

 stimuli, some simple and others complex, involving the inherent tenden- 

 cies and limitations of the organism, antagonistic influences, and all 

 the intricacies of the relationship of an animal to its environment. 



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