120 THE PROGRESS OF SCIENCE n 



speculative " phylogeny," which abounds among 

 my present contemporaries, reminds me very 

 forcibly of the speculative morphology, unchecked 

 by a knowledge of development, which was rife in 

 my youth. As hypothesis, suggesting inquiry in 

 this or that direction, it is often extremely useful ; 

 but, when the product of such speculation is 

 placed on a level with those generalisations of 

 morphological truths which are represented by the 

 definitions of natural groups, it tends to confound 

 fancy with fact and to create mere confusion. We 

 are in danger of drifting into a new " Natur-Philo- 

 sophie " worse than the old, because there is less 

 excuse for it. Boyle did great service to science by 

 his " Sceptical Chemist," and I am inclined to think 

 that, at the present day, a " Sceptical Biologist " 

 might exert an equally beneficent influence. 



Whoso wishes to gain a clear conception of the 

 progress of physiology, since 1837, will do well to 

 compare Miiller's " Physiology," which appeared in 

 1835, and Drapiez's edition of Richard's "Nouveaux 

 Elements de Botanique," published in 1837, with 

 any of the present handbooks of animal and vege- 

 table physiology. Miiller's work was a master- 

 piece, unsurpassed since the time of Haller, and 

 Richard's book enjoyed a great reputation at the 

 time ; but their successors transport one into a 

 new world. That which characterises the new 

 physiology is that it is permeated by, and indeed 

 based upon, conceptions which, though not wholly 



