A Theory of the Parasitic Hahit of the Cuckoo. . 61 



to it have had their short day. That the theory at present 

 most cnrrent is altogether satisfactory, few will maintain ; 

 the following note is suggested as complementary. 



I. Facts. — The general facts which have to be explained 

 are familiar to the omniscient "every schoolboy;" some of 

 the details of minor importance are still debated. Tlie 

 female cuckoo shirks the brooding sacrifice usually associated 

 with bird maternity. But though " she is hardened against 

 her young ones, as though they were not hers," she is not 

 "deprived of wisdom ;" by an elaborate and well-executed 

 trick she foists her several eggs at intervals of a few days 

 into the successive nests of various birds, which are usually 

 insectivorous and suited for the upbringing of the intruder. 

 The foster parents, all unconscious of being fooled, hatch tlie 

 cuckoo egg among their own. The nestling grows rapidly, 

 and is a dog in the manger by birth. Greedy and jealous, 

 he (the masculine pronoun is oftenest correct) soon asserts 

 his monopoly of nest and food and care by the summary 

 eviction of the rightful tenants, whether they be still passive 

 in ovo or more awkwardly assertive as nestlings. The result 

 is the success of the stronger. 



II. Theories. — That the above is a curious instinct, all 

 admit. To some it appears inscrutable, to others only a 

 special instance of a universal method which favours selfish- 

 ness. Or again, one naturalist finds sufficient explanation 

 in certain anatomical conditions which render brooding in- 

 convenient ; but other birds with similar abdominal peculi- 

 arities duly discharge tlieir natural duties. Another refers 

 to the almost unique power the cuckoo has of retaining the 

 eggs, instead of laying them as usual in rapid succession ; 

 but this by itself requires explanation, and is insufficient. 

 Then I find disconnected hints of the view I wish to suocrest 

 in reference by some to the great greed, by others to the 

 preponderance of males. It is necessary, however, to pass to 

 the theory which at present holds the field. 



The Darwinian theory of the parasitic habit emphasises 

 its advantages, and maintains its gradual establishment by 

 the usual process of natural selection. What, then, are the 

 alleged advantages of the habit ? The illustrious Jenncr in 



