IX THE LAST HALF-CEXTURY. 125 



tion, it is often extremely useful ; but, 

 when the product of such speculation is 

 placed on a level with those generalisa- 

 tions of morphological truths which are 

 represented by the definitions of natural 

 groups, it tends to confuse fancy with 

 fact and to create mere confusion. We 

 are in danger of drifting into a new 

 ' Natur-Philosophie ' worse than the old, 

 because there is less excuse for it. Boyle 

 did great service to science by his ' Scep- 

 tical Chemist,' and I am inclined to think 

 that, at the present day, a ' Sceptical 

 Biologist ' might exert an equally benefi- 

 cent influence. 



"Whoso wishes to gain a clear concep- Physiol- 

 tion of the progress of physiology, since ° 

 1837, will do well to compare Muller's 

 'Physiology,' which appeared in 1835, 

 and Drapiez's edition of Richard's ' Nou- 

 veaux Elements de Botanique,' published 

 in 1837, with any of the present hand- 

 books of animals and vegetable physiolo- 



