THOUGHTS ON SPECIES. 161 



diagnosis must be confined to a description of the ornamen- 

 tation of the perfect being, there are no means of distin- 

 guishing certainly the variety from species, should the 

 former differ from the latter essentially in this respect ; and 

 I have no doubt that every effort at systemization with a 

 knowledge of perfect forms alone contains many illustrations 

 of the attendant difficulties of discrimination. 



It is not my desire to enter into any special discussion of 

 this subject ; it is sufficient to enunciate what I believe truth, 

 and apparent to my own mind. Discussions must be founded 

 either on principles or on prejudices ; if the former should 

 differ, there can be no advance until the truth is made ap- 

 parent by a surer mode than that which is so apt to degene- 

 rate into sophistication, and if the latter is the basis on which 

 it is conducted, it is needless to say it never has and never can 

 effect any good. 



While seeking to avoid this latter influence, it will be 

 proper in the present connection to notice, in a very concise 

 manner, the views of an apparently numerous and increasing 

 body of naturalists, who advocate the existence of permanent 

 and geographical varieties, resulting from the effect of phy- 

 sical agencies on the animal organism ; and the tendency, on 

 the other hand, of species and varieties to depart indefinitely 

 from the original type. I cannot but think these opinions 

 have arisen as the consequence of an exceedingly limited 

 view of the nature of species, and from the study and com- 

 parison of perfect beings exclusively. Another obvious source 

 of fallacy in the reasoning by which such views are supported, 

 is to include in the abstract treatment of the nature of species 

 or variety, what we know obtains amongst animals in a state 

 of domestication or civilization ; since it is, at least, a subject 

 of grave doubt, whether domestic varieties have not pro- 



1860. M 



