An Introduction to a Biology 



ning in tubes, or the result of the vibration of molecules, 

 it is certainly true that the more often a certain thought has 

 been formulated the less difficult is it to forget it. The 

 oftener we read a book the better do we know it. Yet this 

 property of the brain has dire consequences. A thought 

 merely by being formulated a great number of times becomes 

 fixed. I am thinking not so much of thoughts that occupy 

 a prominent place in our mind, or thoughts in which we are 

 particularly interested, but of thoughts which occupy a back 

 seat, which are used as a starting-point for trains of thought. 



Sir Harry Johnston had heard about the animal which, 

 we know now as the okapi from the natives, who called it a 

 donkey (doubtless because of its large ears), and this, coupled 

 with the fact that a strip of skin from its rump, which the 

 native soldiers used as bandohers, was beautifully striped, 

 led him to conclude that the animal was a new species of 

 zebra. How long Sir Harry Johnston went on thinking it 

 must be a zebra I do not know. But when he came to explore 

 the forest for this animal, he so little questioned the idea 

 that it could be anything but a zebra, that he abstained 

 from following any artiodactyle spoor he came across be- 

 cause, he thought, it belonged not to the beast he was after, 

 but to some great forest eland. In the light of what we 

 now know of the okapi it is probable that, if the idea that 

 the animal was a zebra had been only just so httle less firmly 

 implanted in his mind as to allow him to try one of the 

 spoors of the cloven hoof, he would have been rewarded by 

 a sight of this wonderful animal. 



It is probably this feature of the mind which makes us 

 so incapable of recognising that a thing which we have come 

 to regard as a starting-point from which we may proceed 

 to the discovery of new things may not really be the starting- 

 point, after all. 



In heredity the theory of unit-characters owes its wide 

 acceptance to-day to the glare of light which has been directed 

 on to Mendelian hereditary phenomena. Some of those who 



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