PROBLEMS OF BIOLOGY 313 



of the proteids ' ; and I think that another physiologist (but 

 I forget who) has declared that the mystery of Life lay 

 hidden in ' the chemistry of the enzymes.' But of late, as 

 Dr Haldane showed in an address a couple of years ago, 

 it is among the physiologists themselves, together with 

 the embryologists, that we find the strongest indica- 

 tions of a desire to pass beyond the horizon of Descartes, 

 and to avow that physical and chemical methods, the 

 methods of Helmholtz, Ludwig, and Claude Bernard, fall 

 short of solving the secrets of physiology. On the other 

 hand, in zoology, resort to the method of experiment, the 

 discovery, for instance, of the wonderful effects of chemical 

 or even mechanical stimulation in starting the development 

 of the egg, and again the ceaseless search into the minute 

 structure, or so-called mechanism, of the cell, these I think 

 have rather tended to sway a certain number of zoologists 

 in the direction of the mechanical hypothesis. 



But on the whole, I think it is very manifest that there is 

 abroad on all sides a greater spirit of hesitation and caution 

 than of old, and that the lessons of the philosopher have had 

 their influence on our minds. We realise that the problem 

 of development is far harder than we had begun to let our- 

 selves suppose : that the problems of organogeny and 

 phylogeny (as well as those of physiology) are not compara- 

 tively simple and well-nigh solved, but are of the most 

 formidable complexity. And we would, most of us, confess, 

 with the learned author of The Cell in Development and 

 Inheritance, that we are utterly ignorant of the manner in 

 which the substance of the germ-cell can so respond to the 

 influence of the environment as to call forth an adaptive 

 variation ; and again, that the gulf between the lowest forms 

 of life and the inorganic world is as wide, if not wider, than 

 it seemed a couple of generations ago. 1 



While we keep an open mind on this question of Vitalism, 



1 Wilson, op. tit., 1906, p. 434. 

 2R 



