Parasitism and Social Reciprocity. 185 



plementing this natural coat with the clothing of his fellow animals 

 from whatever motive or whim at first, came later to be desirable and at 

 last to be necessary to his comfort, and in all but torrid countries essen- 

 tial to his existence, since by the disuse of his own natural clothing he 

 has lost almost the whole of it. In personal prowess, strength of limb, 

 claw and jaw, the man of flocks and herds is no match for a gorilla. 

 The domestic animals have likewise largely lost the power of self help 

 by having so long been wards, and it would go hard with many of them 

 if they were left to their own resources to get their living. They have 

 all been carefully selected and improved by man in the qualities useful 

 to him, but those useful to themselves in a state of nature have been 

 largely lost. 



The parasitic habit of the Cuckoo of laying her eggs always in the 

 nest of another bird, has probably reacted on the tribe in destroying 

 their faculty for building nests. The Molothra, a variety of the Troopial, 

 is another bird that has this habit. 



The English C uckoo is described as a discontented, ill-conditioned, 

 passionate, in short, decidedly unamiable bird." They are unsociable, 

 and migrate alone. The males predominate, being five times as numer- 

 ous as the females, and, according to some authors, more than that. 

 They are very greedy, selfish, and of a gluttonous appetite. The males 

 and females do not pair or mate, in the sense of keeping company, 

 though in the breeding season the males are passionate. The female 

 when adult cannot be distinguished externally from the male. The re- 

 productive organs of both sexes are very small for the size of the bird. 

 The parturition is sluggish, intervals of six or eight days intervening 

 between the laying of the eggs. The eggs are small and are deposited 

 in the nests of insectivorous birds, usually one in each foster nest, but 

 occasionally two. After the young cuckoo is hatched it shows the 

 greedy and selfish disposition of its race by often ousting its foster 

 brothers and sisters from the nest, and monopolizing all the food, and 

 it grows remarkably fast. There is occasional reversion of the English 

 Cuckoo to ' ' ancestral habits, even, in some cases, to apparent affection 

 for the young." 



The American Cuckoo is only occasionally parasitic, but is usually 

 not so careful of and interested in its young as other birds. To work for 

 another begets affection for him. 



It is evident that the parasitic habit is an acquired one, the ancestors 

 of the Cuckoo having, at one time, had the maternal instincts of other 

 birds. The shirking of the maternal function of building the nest, then 

 of caring for the young, &c. , undoubtedly was the cause of the decline 

 of the maternal instincts in the race, the preponderance of the males, 

 their greedy and selfish disposition, the similarity between the sexes, 



