45 o THE POPULAR SCIENCE MONTHLY. 



" Though the instincts of animals appear and disappear in such 

 seasonable correspondence with their own wants and the wants of 

 their oftspring as to be a standing subject of wonder, they have by 

 no means the fixed and unalterable character by which some would 

 distinguish them from the higher faculties of the human race. Tbey 

 vary in the individuals as does their physical structure. Animals can 

 learn what they did not know by instinct, and forget the instinctive 

 knowledge which they never learned, while their instincts will often 

 accommodate themselves to considerable changes in the order of 

 external events. Everybody knows it to be a common practice to 

 hatch duck's-eggs under a common hen, though in such cases the hen 

 has to sit a week longer than on her own eggs. I tried an experiment 

 to ascertain how far the time of sitting could be interfered with in 

 the opposite direction. Two hens became broody on the same day, 

 and I set them on dummies. On the third day I put two chicks a day 

 old to one of the hens. She pecked at them once or twice, seemed 

 rather fidgety, then took to them, called them to her, and entered on 

 all the cares of a mother. The other hen was similarly tried, but 

 with a very diflerent result. She pecked at the chickens viciously, 

 and both that day and the next stubbornly refused to have anything 

 to do with them," etc. 



It would have been well if Mr. Spalding had stated whether these 

 two hens belonged to the same breed ; for, as is of course well known, 

 diiferent breeds exhibit great variations in t]\e chai'acter of the incu- 

 batory instinct. Here, for instance, is a curious case : Spanish hens, 

 as is notorious, scarcely ever sit at all ; but I have one purely-bred 

 one, just now, that sat on dummies for three days, after which time 

 her patience became exhausted. However, she seemed to think that 

 the self-sacrifice she had undergone during these three days merited 

 some reward, for, on leaving the nest, she turned foster-mother to all 

 the Spanish chickens in the yard. These were sixteen in number, and 

 of all ages, from that at which their own mothers had just left them 

 up to full-grown chickens. It is remarkable, too, that although there 

 were Bralima and Hamburg chickens in the same yard, the Spanish 

 hen only adopted those that were of her own breed. It is now four 

 weeks since this adoption took place, but the mother as yet sliows no 

 signs of wishing to cast of her heterogeneous brood, notwithstanding 

 some of her adopted chickens have grown nearly as large as herself. 



The following, however, is a better example of what may be called 

 plasticity of instinct : Three years ago I gave a pea-fowl's egg to a 

 Brahma hen to hatch. The hen was an old one, and had previously 

 reared man}' broods of ordinary chickens with unusual success even 

 for one. of her breed. In order to hatch the pea-chick she had to sit 

 one week longer than is requisite to hatch an ordinary chick, but in 

 this there is nothing very unusual, for, as Mr. Spalding observes, the 

 same thing happens with every hen that hatches out a brood of duck- 



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