14 THE COURTSHIP OF ANIMALS 



as give rise to manes, beards, long plumes, and so on, to 

 a " surplus of strength, vitality and growth-power which 

 is able to expend itself in this way without injury," or, as 

 he sometimes expresses it, to superabundant vitaUty. He 

 was evidently striving to find words for the faith that was 

 in him, and he was nearer the truth than he knew or than 

 his critics supposed. He was seeking facts which only 

 the physiologist could furnish. And these made their 

 appearance long years after with Professor Starling's 

 discovery of Hormones. We are far from understanding 

 the origin of these mysterious juices which must be so 

 frequently alluded to in these pages, but they are evidently 

 intimately associated with the expenditure of energy. 

 This may sometimes find an outlet in increased stature, 

 sometimes in pure luxuries of growth. The force of 

 Wallace's arguments was crushed out by the weight of 

 detail they were made to bear. 



Mr. J. T. Cunningham a few years ago entered the lists 

 and failed to achieve his purpose no less completely. 

 His was a theory which assumed too much. In the first 

 place it was based on the transmissibility of acquired 

 characters, of the truth of which there is at present no 

 evidence. 



He contends, for example, that the vivid hues of scarlet, 

 blue, yellow and violet which colour the naked skin of 

 the neck of the cassowaries and of both sexes, and the 

 curious horny casque which surmounts the head, are 

 the outcome of the constant laceration of the skin inflicted 

 by the males during their conflicts for the possession of 

 the females ,, He assumes that such conflicts take place, 

 and he assumes that such " acquired characters " are 

 transmitted. Now, as a matter of fact, these birds do 

 not fight with their beaks, but with their feet. And to 



