that connect the Orders and Families of Birds. 511 



of things in nature. The very perfection of my plan would in 

 that case be of itself the most formidable obstacle to my convic- 

 tion of its truth and justness. Still, however, sufficient grounds 

 have been shown, I trust, to prove the general prevalence of the 

 principle which it is my wish to establish : and when we see it 

 carried to so considerable an extent ; when we find nothing to 

 contradict it either in the groups which we already know, or in the 

 species which are every day pouring in upon us — we may infer 

 from analogy, I take it for granted, that the principle itself is 

 universal ; and that the deficiencies observable in our series are 

 the result merely of our limited knowledge, and such as we may 

 expect to see remedied as our acquaintance with nature becomes 

 more extended. 



How far the details that have been entered into in the fore- 

 going view of my subject are correct, it is not for me to deter- 

 mine. I myself can detect many alterations that might take 

 place, and many modifications that might be effected, without 

 interfering with the general object of this investigation, or im- 

 pugning the principles which it has been my wish to illustrate. 

 Many of the different groups, for instance, might be enlarged at 

 their extremes by important additions from the conterminous 

 subdivisions, or might on the other hand be contracted by the 

 transfer of a portion of their own extremes to the groups which 

 adjoin them. Intervening assemblages might in like manner be 

 formed out of the extremes on each side, and be separated from 

 both, forming distinct and osculant orders 'or families between 

 them, according to their extent and importance. Where there 

 are no absolute divisions except species in nature, — and this from 

 every observation 1 have been enabled to make I firmly believe 

 to be the case, — every division which we are forced to institute 

 in our arrangements for the convenience of illustration, and in- 

 deed for the purpose of mutual communication with those who 



are 



