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Show 192 INSTINOT. [On.AP. VII. ever been selected for tameness ; and I presume that we must attribute the whole of the inherited change from extreme wildness to extreme tameness, simply to habit, and long-continued close confinen1ent. Natural instincts are lost under domestication : a remarkable instance of this is seen in those breeds of fowls which very rarely or never become "broody," that is, never wish to sit on their eggs. Familiarity alone prevents our seeing how universally and largely the minds of our domestic animals have been modified by domestication. It is scarcely possible to doubt that the love of man has become instinctive in the dog. All wolves, foxes, jackals, and species of the cat genus, when kept tame, are most eager to attack poultry, sheep, and pigs; and this tendency has been found incurable in dogs which have been brought home as puppies from countries such as Tierra del Fuego and Australia, where the savages do not keep these domestic animals. How rarely, on the other hand, do our civilised dogs, even ·when quite young, require to be taught not to attack poultry, sheep, and pigs ! No doubt they occasionally do make an attack, and are then beaten; and if not cured, they are destroyed; so that habit, with some degree of selection, has probably concurred in civilising by inheritance our dogs. On the other hand, young chickens have lost, wholly by habit, that fear of the dog and cat which no doubt was originally instinctive in them, in the same way as it is so plainly iJ?.stinotive in young pheasants, though reared under a hen. It is not that chickens have lost all fear, but fear only of dogs and cats, for if the hen gives the danger-chuckle, they will run (more especially young turkeys) from under her, and conceal themselves in the surrounding grass or thickets; and this is evidently done for the instinctive purpose of allowing, as we see in wild ground-birds, their mother to fly away. But this instinct retained by our chickens has become useless under domestication, for the mother~hen has ahnost lost by disuse the power of flight. Hence, we may conclude, that domestic instincts have been acquired and natural inst~cts have been lost partly 0HAP. VII.] OF 'l'IIE OUOKOO. 193 by ~abit, and :partly by man selecting and accun1ulating du1:rng succ.essive g.enerations, peculiar mental habits and actions, whiCh at first appeared from what we must in our igno~ance call an accident. In some cases compulsory habit alone has sufficed to produce such inherited men~al changes ; in other cases c01npulsory habit has done nothing, and. all has been the ~esult of selection, pursued both methodwally and unconsCiously; but in most cases probably, habit and selection have acted together. ' We shall, perhaps, best understand how instincts in a state of nature have become modified by selection by considering a f~w cases. I will select only three, o~t of the several whwh I shall have to discuss in my future work,-namely, the instinct which leads the cuckoo to lay her egg~ in other birds' nests ; .the slave-making instinct of certain ants; and the c01nb-maldng power of the hive? ee: these two latter instincts have generally, and most JUStly, been ranked by naturalists as the most wonderful of all known instincts. It is now commonly admitted that the more iminediate and final cause of the cuckoo's instinct is that she lays her eggs1 not daily, but at intervals of two ~r 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 ti;me uni~cubated, or .there would be eggs and young birds of different ages In the san1e nest. If this were the cas~, the process of laying. and hatching might be incon- . venwntly long, .more especially as she has to Inigrate 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 asserted that the Ameri~ can cuckoo occasionally lays her eggs in other birds' nests ; . h?-t I ~ear on the high authority of Dr. Brewer, that th1s IS a mistake. Nevertheless I could O'ive several . t f . ' 5 I~s ances o varrous birds which have been known occa- Sionally to lay their eggs in other birds' nests. Now let us suppose that the ancient progenitor of our Europea11 cuckoo had the habits of the American cuckoo· but that 9 ' . |