310 MENTAL EVOLUTION IN ANIMALS. 



of doubt, and even if the phenomena of kataplexy were not 

 available for natural selection to seize upon for the purpose 

 in question, there can be no doubt that other materials 

 might have been so ; for, a priori, there seems to be at least 

 not more difficulty in developing an instinct to remain 

 motionless under certain circumstances, than in developing 

 one to run away ; and as a matter of fact, all animals which 

 are protectively coloured have, either as cause or consequence, 

 developed their instincts in the former direction. Therefore 

 we must suppose that an animal which was not sufficiently 

 locomotive to find safety in flight, would be most closely 

 attended to by natural selection in the direction of encourag- 

 ing quiescence — and this whether or not natural selection 

 were provided with kataplectic susceptibilities on which to 

 operate ; kataplexy alone could not form the instinct. 



So far, then, the subject is sufficiently clear. But now, 

 we have obviously some important distinctions to draw. For 

 the shamming dead of a highly intelligent animal like a fox 

 is a widely different matter, psychologically considered, from 

 the shamming dead of insects ; so that an explanation which 

 might be held fully adequate to account for the latter might 

 not be so to account for the former. Thus while I have no 

 hesitation in regarding the fact in insects as due to a non- 

 intelligent instinct developed by natural selection in the way 

 just explained, I cannot see how this could well be the case 

 in vertebrated animals. A fox would never have so good a 

 chance of escape from an enemy by remaining motionless as 

 it would by the use of its legs, which it requires a fox-hound 

 to overtake. Moreover the shamming dead is here far from 

 invariable, and so is not, as in the case of insects, instinctive. 

 Therefore, although I did not fully agree with Preyer in 

 assigning the universal (instinctive) quiescence of certain 

 insects when alarmed to the unassisted influence of kata- 

 plexy, I think that the occasional (accidental) display of 

 quiescence by wild vertebrated animals under similar circum- 

 stances tends much more unequivocally in favour of his view. 

 Tor here the action is not universal, or even usual ; and when 

 it does take place it must, as a rule, be rather detrimental to 

 the animal than otherwise — seeing that the whole economy of 

 the animal is here adapted to rapid movement. Therefore 1 

 think that in the case of Birds and Mammals the hypothesis 

 of Couch already quoted is the most reasonable — especially 



