THE ZOOLOGIST 



THIRD SERIES. 



Vol. XVII.] OCTOBER, 189 3. [No. 202. 



DIFFERENTIATION, MIGRATION, AND MIMICRY. 

 By the Rev. H. B. Tristram, M.A., LLD. } F.R.S.* 



It is difficult for the mind to grasp the advance in biological 

 science — I use the term biology in its wide etymological, not its 

 recently restricted sense — which has taken place since I first 

 attended the meetings of the British Association, some forty years 

 ago. In those days, the now familiar expressions of "natural 

 selection," "isolation," "the struggle for existence," "the survival 

 of the fittest," were unheard of and unknown, though many an 

 observer was busied in culling the facts which were being poured 

 into the lap of the philosopher who should mould the first great 

 epoch in natural science since the days of Linnaeus. 



It is to the importance and value of field-observation that 

 I would venture in the first place to direct )'our attention. 



My predecessors in this chair have been, of recent years, 

 distinguished men who have searched deeply into the abstrusest 

 mysteries of physiology. Thither I do not presume to follow them. 

 I rather come before you as a survivor of the old-world naturalist, 

 as one whose researches have been, not in the laboratory or with 

 the microscope, but on the wide desert, the mountain side, and 

 the isles of the sea. 



This year is the centenary of the death of Gilbert White, 

 whom we may look upon as the father of field-naturalists. It is 



* Presidential Address to the Biological Section of the British Association, 

 at Nottingham, September, 1893. 



ZOOLOGIST. — OCTOBEB, 1893. £ F 



