234 THE PLAY OF ANIMALS. 



If, then, colouring is connected with nerve distri- 

 bution it must be largely dependent on good health, 

 and brilliant colour becomes an indication of robust 

 health. This is true also of other kinds of external or- 

 namentation, especially of the size of the tail. The per- 

 fect adaptation of animals to their environment pro- 

 duces in them a superabundance of vigour which con- 

 tributes to the size and brilliance of plumage that 

 we admire in such birds as the pheasant, parrot, hum- 

 ming bird, etc. To the question why this is the case 

 with males alone it may be answered that the female 

 has the greater need of protection. This view is sup- 

 ported by the fact that in general, female birds of those 

 species that have well-protected nests are as brightly 

 coloured as the males. 



Wallace applies this principle to skill in flight and 

 dancing as well as to ornamentation, the same prin- 

 ciple of superabundant energy which we found in the 

 Schiller-Spencer theory of play. " The display of these 

 plumes will result from the same causes which led to 

 their production. Just in proportion as the feathers 

 themselves increased in length and abundance, the skin 

 muscles which serve to elevate them would increase also; 

 and the nervous development, as well as the supply of 

 blood to these being at a maximum, the erection of the 

 plumes would become a habit at all periods of nerv- 

 ous or sexual excitement." ..." During excitement 

 and when the organism develops superabundant energy, 

 many animals find it pleasurable to exercise their vari- 

 ous muscles, often in fantastic ways, as seen in the gam- 

 bols of kittens, lambs, and other young animals. But 

 at the time of pairing male birds are in a state of the 

 most perfect development, and possess an enormous 

 store of vitality; and under the excitement of the sexual 



