30 THE PRINCIPLE OF Chap. I. 



manner of flight of certain breeds of the pigeon, &c. 

 We have analogous cases with mankind in the inheritance 

 of tricks or unusual gestures, to which we shall presently 

 recur. To those who admit the gradual evolution of 

 species, a most striking instance of the perfection with 

 which the most difficult consensual movements can be 

 transmitted, is afforded by the humming-bird Sphinx- 

 moth (Macroglossa) ; for this moth, shortly after its 

 emergence from the cocoon, as shown by the bloom on its 

 unruffled scales, may be seen poised stationary in the 

 air, with its long hair-like proboscis uncurled and 

 inserted into the minute orifices of flowers; and no 

 one, I believe, has ever seen this moth learning to 

 perform its difficult task, which requires such uner- 

 ring aim. 



When there exists an inherited or instinctive tend- 

 ency to the performance of an action, or an inherited 

 taste for certain kinds of food, some degree of habit 

 in the individual is often or generally requisite. We 

 find this in the paces of the horse, and to a certain extent 

 in the pointing of dogs; although some young dogs point 

 excellently the first time they are taken out, yet they 

 often associate the proper inherited attitude with a 

 wrong odour, and even with eyesight. I have heard 

 it asserted that if a calf be allowed to suck its mother 

 only once, it is much more difficult afterwards to rear 

 it by hand. 3 Caterpillars which have been fed on the 

 leaves of one kind of tree, have been known to perish 

 from hunger rather than to eat the leaves of another 

 tree, although this afforded them their proper food, 



3 A remark to much the same effect was made long - ago 

 by Hippocrates and by the illustrious Harvey; for both 

 assert that a young* animal forgets in the course of a few 

 days the art of sucking, and cannot without some diffi- 

 culty again acquire it. I give these assertions on the au- 

 thoritvof Dr. Darwin, ' Zoonomia,' 1794, vol. i. p. 140. 



