1899] THE STUDY OF NATURAL HISTORY 445 



ships, its complex inter-adaptations, and its strange tnrns and twists of 

 individual development, we must look for light in the inconceivably 

 distant past. Just as we may see to read by the fireside of to-day by 

 a light which is obviously the transformed sunshine of the carbon- 

 iferous era, so the animal life of the past illumines that of the present, 

 and it is on this account chiefly that we study it. To take a concrete 

 instance, the migration of birds is a fascinating and extremely puzzling- 

 problem in natural history, the solution of which is still far off; but 

 it will be admitted by most that the facts have become in certain 

 aspects more intelligible by being considered in connection witli the 

 evolution of climates and with the great Ice Age in particular. 



The Fourth Question, 



There remains a fourth question, also ancient, but now asked with 

 a new hopefulness — " How have these living creatures come to be as 

 they are ? " They have had a history — a slow racial evolution — as 

 surely as they have an individual development ; what have been the 

 factors in this history ? How has the raw material of progress, which 

 we call variation, been made available throughout the countless ages ? 

 and how has this raw material been fashioned to shape and use ? We 

 have got a firm grasp of a modal interpretation — that the present is 

 the child of the past — but we must beware of confusing this with a 

 causal theory. The idea of evolution is the most potent thought- 

 economising formula which the world has yet known, but as to the 

 factors in the evolution we are still only inquiring. 



I have said that there cannot now be a stable and progressive 

 natural history which does not ask the three questions — What is this ? 

 How does it act ? Whence has it come ? — which does not, in other 

 words, recognise the methods and results of morphology, physiology, 

 embryology, and palaeontology ; but I do not say that all useful 

 natural history work must have this completeness of inquisitiveness or 

 outlook. History would contradict this, though I doubt whether any 

 of the immortals on the roll-call of naturalists did not in his fashion 

 ask all the questions. It is plain, however, that Eeaumur was little 

 concerned about the palaeontology of insects, and that Gilbert White 

 knew nothing of the embryology of the earthworm. It is plain that 

 Christian Konrad Sprengel was not much interested in histology, and 

 that Buffon knew little of the physiology of the individual. Yet all 

 the four were such splendid naturalists that it seems almost an im- 

 pertinence to praise them. Just as I presume no one would deny the 

 artistic mood to the author of a picture which was exquisite in form 

 but weak in colour, or of another which was feeble in its form but a 

 joy for ever in its colour, so we reverence the old naturalists none the 

 less in admitting their limitations. 



This saving paragraph is necessitated by the fact — the historical 



