2i8 THE POPULAR SCIENCE MONTHLY. 



of animal instincts. These instincts must originally have been of an 

 intelligent nature ; but the actions which they prompted, having through 

 successive generations been frequently repeated, became at last organ- 

 ized into a purely mechanical reflex, and therefore now appear as actions 

 which we call purely automatic or blindly instinctive. Thus, for in- 

 stance, the scratching of graminivorous birds in earth and stones was 

 no doubt originally an intelligent aotion, performed with the conscious 

 purpose of uncovering seeds ; but by frequent repetition through suc- 

 cessive generations the action has now become blindly instinctive. This 

 is shown by the following experiment : Dr. Allen Thomson tells me 

 that he hatched out some chickens on a carpet, where he kept them for 

 several days. They showed no inclination to scratch, because the stimu- 

 lus supplied by the carpet to the soles of their feet was of too novel a 

 character to call into action the hereditary instinct ; but when Dr. 

 Thomson sprinkled a little gravel on the carpet, and so supplied the 

 appropriate or customary stimulus, the chickens immediately began 

 their scratching movements. Yet, for aught that these chickens can 

 have known to the contrary, there was as good a chance of finding seeds 

 in the carpet as in the thin layer of gravel. And numberless other 

 cases might be given to prove that animals acquire instincts by fre- 

 quently repeating intelligent actions, just as we ourselves acquire, even 

 in our individual lifetime, an instinct to adjust our nightcaps — an in- 

 stinct which may become so pronounced as to assert itself even when a 

 man is in the profound unconsciousness of apoplectic coma. 



Thus we are able to explain all the more complicated among ani- 

 mal instincts as cases of "lapsed intelligence." But, on the other 

 hand, a great many of the more simjole instincts were probably evolved 

 in a more simple way. That is to say, they have probably never been 

 of an intelligent character, but have begun as merely accidental ad- 

 justments of the organism to its surroundings, and have then been laid 

 hold upon by natural selection and developed into automatic reflexes. 

 Take, for instance, the action of so-called " shamming dead," which is 

 performed by certain insects and allied animals when in the presence 

 of danger. That this is not a case of intelligent action we may feel 

 quite sure, not only because it would be absurd to suppose that insects 

 could have any such highly-abstract ideas as those of death and its con- 

 scious simulation, but also because Mr. Darwin tells me that he once 

 made a number of observations on this subject, and in no case did he 

 find that the attitude in which the animal shammed dead resembled 

 that in which the animal really died. All, therefore, that " shamming 

 dead " amounts to is an instinct to remain motionless, and therefore in- 

 conspicuous, in the presence of enemies ; and it is easy to see that this 

 instinct may have been developed by natural selection without ever 

 havins; been of an intellisfent nature — those individuals which were 

 least inclined to run away from enemies being preserved rather than 

 those which rendered themselves conspicuous hj movement. 



