MAESH WARBLER 



tion of the difference lies outside the province of utility 

 indicated by Professor G-roos ; there must be some other 

 factor which, exercising independent control, arrests develop- 

 ment here or allows it to proceed there to the verge of 

 extravagance. I therefore suggest that the reactions may be 

 by-products of this factor which regulates the intensity of the 

 activity feelings, and that after all there may be something 

 to be said for the third proposition — the view that would 

 regard them as having arisen independently of any question 

 of utility. The infinite number of specific types of reaction 

 lends some support to this view. How frequently we can 

 distinguish a species merely by some particular way in which 

 it behaves in the breeding season ! The Greenfinch, Yellow 

 Bunting, Tree Pipit, Meadow Pipit, Snipe, Huff, Kedshank, 

 Black-tailed Godwit and a host of others we can recognise, 

 each one by its own particular mode of conduct. The reac- 

 tions reflect the emotions — says the " utility " hypothesis — 

 excite the female and are thus of some use, but why should 

 they have taken the form of a spreading of the tail in this 

 case, a waving of wings in that, or a fluttering in mid-air in 

 a third? It is evident that there is something here which 

 requires an explanation if we regard them thus, and it is 

 evident that the assistance of some further factor, which can 

 guide the reactions into certain definite channels, must be 

 assumed in order to complete the explanation. In one pas- 

 sage Professor Grroos seems to recognise the difficulty of 

 attributing utility to the reactions and almost approaches the 

 conclusion that they may be but incidents of the nervous 

 system having no special part to fulfil. 1 " We must admit," 

 he says, " that in most cases the actual basis for the arts of 

 courtship is to be found in general excitement reflexes, or 

 even in those of quite a different origin. This basis consists 

 partly in such reflex motions as result from any strong excita- 

 tion such as restless fluttering, running about, skipping and 



1 " The Play of Animals," p. 247. 



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