PLASTICITY OF INSTINCT. 451 



lings.' The object with which I made this experiment, however, was 

 that of ascertaining whether the period of maternal care subsequent 

 to incubation admits, under peculiar conditions, of being prolonged ; 

 for a pea-chick x-equires such care for a very much longer time than 

 does an ordinary chick. As the separation between a hen and her 

 chickens always appears to be due to the former driving away the lat- 

 ter when they are old enough to shift for themselves, I scarcely expect- 

 ed the hen in this case to prolong her period of maternal care, and in- 

 deed only tried the experiment because I thought that if she did so the 

 fact would be the best one imaginable to show in what a high degree 

 hereditary instinct may be modified by peculiar individual experiences. 

 The result was very surprising. For the enormous period of eighteen 

 months this old Brahma hen remained with her evex'-growing chicken, 

 and throughout the whole of that time she continued to pay it unre- 

 mitting attention. She never laid any eggs during this lengthened 

 period of maternal supervision, and, if at any time she became acci- 

 dentally separated from her charge, the distress of both mother and 

 chicken was very great. Eventually the separation seemed to take 

 place on the side of the peacock; but it is remarkable that, although 

 the mother and chicken eventually separated, they never afterward 

 forgot each other, as usually appears to be the case with hens and 

 their chickens. So long as they remained together the abnormal de- 

 gree of pride which the mother showed in her wonderful chicken was 

 most ludicrous ; but I have no space to enter into details. It may be 

 stated, however, that both before and after the separation the mother 

 was in the habit of frequently combing out the top-knot of her son 

 she standing on a seat, or other eminence of suitable height, and he 

 bending his head forward with evident satisfaction. This fact is par- 

 ticularly noteworthy, because the practice of combing out the top- 

 knot of their chickens is customary among pea-hens. In conclusion, I 

 may observe, that the peacock reared by this Brahma hen tui-ned out 

 a finer bird in every way than did any of his brothers of the same 

 brood which were reared by their own mother, but that, on repeating 

 the experiment next year with another Brahma hen and several pea- 

 chickens, the result was different, for the hen deserted her family at 

 the time when it is natural for ordinary hens to do so, and in conse- 

 quence all the pea-chickens miserably perished. 



I have just concluded another experiment which is well worth 

 recording : A bitch ferret strangled herself by trying to squeeze 

 through too narrow an opening. She left a very young family of 

 three orphans. These I gave, in the middle of the day, to a Brahma 

 hen which had been sitting on dummies for about a month. She took 

 to them almost immediately, and remained with them for rather more 



' The greatest prolongation of the incubatory period I have ever known to occur was 

 in the case of a pea-hen which sat very steadily on addled eggs for a period of four 

 months, and had then to be forced oflF in order to save her life. 



