II. WHAT IS A SPECIES? 39 



— then, it seems quite logically to follow, that the 

 existence of species in nature is equally an inference or 

 supposition, and not a certain fact, so far as human 

 knowledge yet reaches. 



This appears to be the actual condition of technical 

 botany. The existence of real species, according to a 

 strict definition of the term, has not been fully and logi- 

 cally proved. But it is assumed and believed to be a 

 truth, because the arguments advanced in support of the 

 previously assumed truth, under present knowledge, ap- 

 pear to be more weighty, and more nearly conclusive, 

 than any which are adduced against the belief. It may 

 be said further, that such arguments appear thus weighty 

 and conclusive, not solely to the unreasoning minds of 

 the mere describers of species, but also to the minds of 

 many highly reasoning men. Though the latter, be it 

 here observed, are not usually adepts in the knowledge of 

 species so-called ; and they must thus rely rather too 

 much uj^on the representations of the species-men, for 

 the data from which their conclusions or convictions are 

 deduced. 



Now, what do we truly intend by this slippery term 

 Species ? In the ' Geographie Botanique,' after passing 

 under notice various other definitions, M. Alphonse De 

 CandoUe substitutes for them the following one, as his 

 own suggested modification. It is here rather freely than 

 literally rendered in English. He writes, — 



" I admit vegetable species as they present themselves 

 in our own time, and with data from observation during 

 some ages onl)"-, that is to say, as groups of individuals 

 with sufiicient mutual resemblance, — {firstly) to have in 

 common numerous and important characters, which are 

 permanent during several generations, under the influence 



