in Natural H in for!/. 483 



can communicate to his neighbour his perception of their dif- 

 ferences. Thus botanists speak of certain species of plants dif- 

 fering in appearance, habit, touch, &c. ; by which they often 

 mean that they have some indescribable peculiarities about them, 

 which point them out to the practised observer as distinct. A 

 great number of such species may be detected in every modern 

 Flora of a well investigated country ; but whether they deserve 

 to be ranked among those which are capable of definition, is a 

 question of great doubt : — that the practice is an inconvenience, 

 none will deny ; and if it be much longer continued, will involve 

 in inextricable difficulty all our well known species, make us 

 dependent upon empirical and traditional evidence for our ac- 

 quaintance with them, and render it impossible to derive instruc- 

 tion from books. In such cases the assumed law ought to be 

 brought to thetestof experiment, or the species should be rejected. 



Many of our cultivated plants also tend to invalidate the law. 

 AVho can refer our ccrealia and esculent vegetables, in many 

 instances, to their true types ? and how few of our old tlowers 

 are there, of which the astutest botanist can trace the origin ! 

 Domesticated animals aftbrd a still more striking example ; 

 and man himself furnishes the most difficult problem of all. 



These remarks and examples are, I apprehend, sufficient to 

 show how difficult it is to adopt the term in its strict acceptation ; 

 and that however precisely the naturalist has attempted to em- 

 ploy it, he has not succeeded to the extent he has proposed ; and 

 that it can only be taken as correct in a vague and general sense, 

 and as a convenient abstraction to relieve him at the first step 

 from the necessity of becoming acquainted with every individual. 



The next term of importance to the naturalist upon which the 

 accuracy of his reasoning depends, is that division of his system 

 which he denominates a Genus. This is an assemblage of in- 

 dividuals ao-reeinsi; also in some common characters ; but, unlike 



the 



