1899] THE STUDY OF NATURAL HISTORY 447 



the possessor of a master-key, but some new lock has baffled him, and 

 it seems likely that this will be his experience for many years to come. 

 In one of his essays, Professor Weismann rejects the common opinion 

 which compares science to a building resting on sure foundations and 

 rising from a firm basement safely to the highest story ; on the con- 

 trary, he says of the exact sciences — " They all build from above, and 

 not one of them has found a basement yet — not even physics." 



An Illustration. 



Let us now consider a single fact of natural history so that we 

 may see more clearly how an understanding of it makes demands on 

 all the resources of our discipline. It is well known that the mole 

 stores earthworms for use in winter — as many as a hundred being 

 sometimes found together ; it is a less familiar fact that these stored 

 earthworms are, in many cases at least, decapitated, so that although 

 alive they are unable to crawl away. We may begin by asking how 

 the mole and the earthworm happen to be both underground, which is 

 certainly not the primitive home of their respective races ; we pass on 

 to inquire how the mole catches the earthworms, and how they are 

 often able to avoid the mole ; another query raises the problem of the 

 storing instinct ; a side question leads us to consider the mole's im- 

 perfect lenses and the peculiarity of its optic nerves ; then we are 

 bound to inquire how it is that the decapitation of the earthworm 

 prevents its crawling away ; and this brings us to consider the function 

 of the head-ganglia as a motor centre. We know that in summer a 

 lost head-end may be re-grown, but that this does not occur in the low 

 temperature of winter, a fact that raises the whole difficult problem of 

 regeneration ; we know that the re-grown anterior part sometimes 

 turns out to be a second tail instead of a new head, which forces us to 

 face the fact that there are limits to the perfectness of adaptations. 

 We cannot avoid inquiring, too, how far the mole's destruction of 

 earthworms, which are for the most part valuable agriculturally, is 

 compensated for by its destruction of injurious insects. And so from 

 the unearthed store of earthworms in the mole's burrow we pass to 

 problems of nerve physiology, comparative psychology, conditions of 

 development, rural economy, and what not — inquiries which surely 

 become more real and interesting to investigator and student alike 

 when they are centred round an everyday fact of natural history. 



The Essence of Natural History. 



When in our anatomical or zootomical studies we propose to dis- 

 sect the skate or the snail, or the like, we must first isolate it from its 

 environment and kill it ; in other words, we have to make an abstrac- 

 tion — a very necessary and valuable one, but still an abstraction. 



