276 THE EVOLUTION OF SEX. 



reason, we are justified in setting down the instinct to the 

 creating influence of natural selection." 



But against the supposition that a mere freak has been 

 fostered by selection into a habit, it must be noticed that the 

 trick, to be successful, must be played with some care. It is 

 hardly on a par wMth the casual use made by a partridge of a 

 l)heasant's nest, or by a gull of an eider duck's. Again, the 

 advantages to the parent, apart from that of trouble saved, are 

 somewhat dubious. Food, Macgilivray says, remains abundant, 

 and the climate which does not injure the young for two 

 months longer could hardly incommode the parents. Nor is 

 the case improved outside the British area. To suppose, on 

 the other hand, that the advantage to the young has formed 

 the utilitarian basis, is involved in difficulties. We cannot 

 suppose that the mother bird had or has a careful forethought 

 of the best for her offspring in sending them out to nurse. 

 Nor is it easy to see how the comfort of fostered youth will 

 remain as an impulse to the adult to do the like for her young 

 in turn. The difficulty as to the inheritance of such a freak, 

 especially with the preponderant majority of males, is certainly 

 appreciable. The common difficulty of the combination of 

 happy circumstances required to ensure incipient success is 

 unusually great ; the young bird has its part to play as well as 

 the parent ; the habit is not generic, yet obtains in related 

 genera, and also in the widely separated starling-like cow-birds. 



A truer view of the habit is that which considers it as a 

 deliberate expression of the whole constitution of the bird. 



(i.) The general character of the cuckoo is very significant. 

 Brehm describes it as a "discontented, ill-conditioned, pas- 

 sionate, in short decidedly unamiable bird." " The note itself, 

 and the manner in which it is emitted, are typical of the bird's 

 habits and character. The same abruptness, insatiability, 

 eagerness, the same rage, are noticeable in its whole conduct." 

 The cuckoos are notoriously unsociable, even in migration 

 individuahstic. They jealously guard their territorial " pre- 

 serves," and verify in many ways the old myth that they are 

 si)arrow-hawks in disguise. The parasitic habit is consonant 

 with their general character. 



(2.) The species consists predominantly of males. The 

 preponderance is probably about five to one, though one observer 

 makes it five times greater. In so male a species, it is not 

 surprising to find degenerate maternal instincts. 



