INSTINCT 21S 



Hence, we may conclude that under domestication instincts 

 have been acquired and natural instincts have been lost, partly by 

 habit and partly by man selecting and accumulating, during suc- 

 cessive generations, peculiar mental habits and actions, which at 

 first appeared from what we must in our ignorance call an acci- 

 dent. In some cases compulsory habit alone has sufficed to pro- 

 duce inherited mental changes. In other cases compulsory habit 

 has done nothing, and all has been the result of selection, pursued 

 both methodically and unconsciously; but in most cases habit and 

 selection have probably concurred. 



SPECIAL INSTINCTS 



We shall, perhaps, best understand how instincts in a state of 

 nature have become modified by selection, by considering a few 

 cases. I will select only three, namely, the instinct which leads the 

 cuckoo to lay her eggs in other birds' nests; the slave-making in- 

 stinct of certain ants; and the cell-making power of the hive-bee. 

 These two latter instincts have generally and justly been ranked 

 by naturalists as the most wonderful of all known instincts. 



INSTINCTS OF THE CUCKOO 



It is supposed by some naturalists that the more immediate 

 cause of the instinct of the cuckoo is that she lays her eggs, not 

 daily, but at intervals of two or three days, so that if she were to 

 make her own nest and sit on her own eggs, those first laid would 

 have to be left for some time unincubated, or there would be eggs 

 and young birds of different ages in the same nest. If this were the 

 case, the process of laying and hatching might be inconveniently 

 long, more especially as she migrates at a very early period, and 

 the first hatched young would probably have to be fed by the male 

 alone. But the American cuckoo is in this predicament, for she 

 makes her own nest and has eggs and young successively hatched, 

 all at the same time. It has been both asserted and denied that the 

 American cuckoo occasionally lays her eggs in other birds' nests; 

 but I have lately heard from Dr. Merrill, of Iowa, that he once 

 found in Illinois a young cuckoo, together with a young jay, in the 

 nest of a blue jay (Garrulus cristatus) ; and as both were nearly 

 full feathered, there could be no mistake in their identification. I 

 could also give several instances of various birds which have been 

 known occasionally to lay their eggs in other birds' nests. Now let 

 us suppose that the ancient progenitor of our European cuckoo 

 had the habits of the American cuckoo, and that she occasionally 

 laid an egg in another bird's nest. If the old bird profited by this 



