THOUGHTS ON SPECIES. 159 



and are not only similar to it, but identical amongst them- 

 selves. The mind can detect no essential differences on which 

 to establish distinctions, and we recognize them as the same 

 beings, the same conception, whatever may be their geogra- 

 phical origin ; all structural differences have disappeared, 

 and investigation proves that each individual repeats and 

 reiterates one and the same biography with all its distinctive 

 peculiarities. 



The identity of natural bodies of the same species must, 

 however, be received with certain limitations. In no portion 

 of the organic or even the physical world does nature work 

 within the limits of inflexibly parallel lines, but mingles with 

 her laws of harmony or invariability laws of disorder, which 

 affect the most stupendous and apparently most stable of 

 her works, as well as the most humble and insignificant, if 

 anything in nature can be so regarded. Thus, in consider- 

 ing specific life in the humble forms under view, we must 

 allow a limit of variability or disorder, by which constancy 

 in results are affected or apparently deranged, but within 

 circumscribed boundaries. The subject of variation in insects 

 has been so imperfectly investigated, and so many startling 

 theories have been promulgated respecting it, founded on 

 what I must regard as mistaken conceptions respecting the 

 nature of species, that, although we have no special investi- 

 gations to offer on the question, we can at least clear and 

 define our conceptions with respect to what should be re- 

 garded a variety of a species. 



From what has been heretofore said respecting species, we 

 cannot suppose a variety can be detected simply from the 

 study of the perfect insect in its most aberrant condition. 

 For wherein does a variety differ from the species? Is it 

 by any difference in the ovum, any peculiarity in the form, 



