FACTS AND FINDINGS 43 



what they consider the most important problems still 

 unsolved. 



All are agreed that no problem has been fully solved, 

 but that, nevertheless, much light has been thrown upon 

 a good many points of interest which will prove valuable 

 for workers of the future in continuing from where we 

 of this generation have left off. 



It may afford the layman an interesting insight into 

 the mind and thought of the biologist to read a letter such 

 as this: 



''You ask my opinion as to the most important biolog- 

 ical problems of our age! I must confess that I find it 

 utterly difficult to give an exact answer: Any biological 

 problem is of importance, none is superfluous or even of 

 subordinate importance; that is, if you think of biology 

 as a whole and not only as an aid to industry, etc. Biology 

 is a building that needs every one of its stones — if you 

 take any one of them away the entire building will fall 

 into pieces again. Every biological investigation is of 

 equal importance; i.e., if it is not worked out or followed 

 out into caricature. Only history can, in the long run, 

 decide and estimate with certainty the sound kernel of 

 each 'mode' — every 'mode' is bound to be driven into 

 caricature, when its adorers take the last steps into that 

 cul-de-sac, where every mania soon or later comes to an 

 end. Choose whichever instance you will, systematics 

 and classification, phylogeny, cytology, physiology, hered- 

 ity, etc., you will, in every case, find that students of biol- 

 ogy at last put their heads into the cul-de-sac and cannot 



