156 Darwin and Romanes dealt with. 



Promiscuity, carried beyond a very definite point, 

 everywhere is adverse to fertility. So far as practice 

 or experiment can be called in to aid us here, it is 

 absolutely confirmatory. The rabbit is one of the 

 most fertile of creatures ; but is so fertile because it 

 is so observant of this rule. Here is a proof of it, 

 as far as proofs can be got in such matters as these ; 

 when we are concerned with wild creatures more 

 especially. One method of exterminating rabbits, 

 which is said to be found highly successful, is to trap 

 as many as possible, kill off all the does that are 

 caught, and let the bucks loose. " The results of 

 this mode of operation are that the male rabbits, as 

 soon as they begin to predominate in numbers, per- 

 secute the females with their attentions, and prevent 

 them from breeding. They also kill the young rabbits 

 that happen to be born, and even, as Mr. Rodier 

 asserts, when they largely predominate in numbers, 

 worry the remaining does to death." * 



By the way, notice here in animal life, that excess 

 of males, or polyandrous promiscuity, is not only 

 adverse to progeny by arrest of conception, but is 

 favourable to infanticide. 



Now, in the case of the cuckoo, it really seems as 

 though we have an exception to this great law of 

 Nature. The stimulus to the rejection of the male 

 advances by the hen is the attraction to brooding. 

 The cuckoo does not brood, therefore it has no pause 

 of this kind to the desire for contact with the male. 

 If under contact with many males it goes on un- 

 interruptedly laying eggs, this, having regard to all 



* Nature, vol. xxxix, p. 493, quoted by Coe in " Nature versus 

 Natural Selection." 



