EVOLUTION 929 



rest in the open plain and the wild cattle under the shelter of the 

 iorest or thicket. More convincing, we think, is the persistence of 

 the mare's habit of giving her foal many short drinks, while the 

 cow gives her calf a very long drink at a time. There is a physiological 

 reason for this, as for the way an animal rises, but both have also to 

 do with habits and surroundings, and the difference becomes more 

 intelligible when we recall the fact that the troop of wild horses 

 shifts often from place to place, and that the foal has to stagger 

 after its mother soon after birth, so that a big meal would be inap- 

 propriate. But it is different with the calf hidden away in the 

 thicket, to which its mother returns to chew the cud. For our present 

 purpose the interesting fact is the persistence of the difference in 

 habit after it lost no small part of its significance in conditions of 

 domestication. 



Why does a horse shy? At a sudden rustle in the hedgerow, or 

 before a wind-borne ball of paper, it suddenly swerves and may 

 unseat the careless rider, or even upset the gig. There can be little 

 doubt as to the meaning of this nervous trick. It is almost certainly 

 a reawakening of an ancient "reflex", that is to say, an involuntary 

 automatic jerk, which would save the wild horse from being bitten 

 by a snake or pounced on by some lurking carnivore. The profitable 

 reaction in ancient days was to make a sudden swerve away from 

 the rustle or movement. Sometimes, no doubt, the individual horse 

 is very high-strung, and sometimes there has been an individually 

 experienced scare; but for most cases the historical interpretation 

 is sound. The hand of the past on the present is not dead, but 

 living. 



We must not think of these reawakenings as like our own recollec- 

 tions, where genuine memory is concerned. For true memory is 

 the mental revival of a previous individual experience, such as an 

 image, or an impression, or an idea of some sort. But the shying 

 horse on the road and the sleepy dog on the hearthrug illustrate an 

 enregistration of their ancestors' experience, not a memory of their 

 own. No clear-cut dividing line can be drawn in such cases between 

 the bodily and the mental, but the grip of the past that we are 

 illustrating has doubtless more to do with inborn nerve-and-muscle 

 linkages than with the revival of mental images. Let us take more 

 examples. 



The donkey is the domesticated descendant of the Wild Ass of 

 North Africa, and its unwillingness to cross the smallest stream of 

 water is probably a persistent outcrop of prejudices and preferences 

 established long ago in the dry desert. Perhaps its fondness for 

 rolling in the dust has a similar historical origin; but there is no 

 need to overwork the idea. Darwin wrote: "The same strong dislike 

 to cross a stream is common to the camel, which has been domesti- 

 cated from a very ancient period. Young pigs, though so tame, 



VOL. II o 



