Northern Entomological Society. 



8251 



and I uow propose to lay before you the insects which, to my thinking, as nearly 

 demonstrate the truth of that theory as demonstration can be arrived at. In the first 

 place, I lay before you a series of North-American Lepidoptera, collected chiefly by 

 the late Mr. E. Doubleday, and putting-, as. far as I am able, the European analogues 

 side by side, you will see a striking illustration of the common phrase, ' the same with 

 a difference.' Several years before the death of the late Mr. J. F. Stephens, I was 

 talking with him on the subject of these very specimens, when he told me a friend had 

 one day brought to him, by way of a joke, a box of United States Lepidoptera, they 

 being the analogues of British species, when, on opening the box, believing them to 

 be British, his involuntary exclamation was, 'What a wonderful assemblage of 

 varieties.' 



" It must be very far back in point of time, although perhaps, geologically speaking, 

 of recent date, that the Atlantic was so far bridged oyer, as that the individuals of any 

 race of insect could interbreed, and thus render the bias of mutation, to a certain 

 extent, uniform throughout the larger area. We have, in the difference between the 

 parallel forms now exhibited, a measure of the effects of separation through a very 

 long period of time, and when we see, however decided the difference in minor 

 characteristics, how slight is still the separation of form from form, we need not wonder 

 that no appreciable difference can be found between the figures of the ostrich on 

 ancient Eastern monuments and the bird itself still living, under the same circum- 

 stances of climate and food that surrounded it three thousand years ago, and of which 

 fact Mr. Westwood makes so strong a point in favour of the permanency of species. 



"The other specimens exhibited are Nebria and Calathus from the Shetland Isles. 

 They will all be found to differ, to an appreciable extent, from specimens captured 

 on the mainland of Britain. It is probable that the separation of these areas took 

 place at a much later date than the epoch of the separation of North America from 

 Europe. It would therefore have been interesting to have compared the Lepidoptera 

 of Shetland and Britain, only that the distance to which the islands are removed from 

 each other is so small as to vitiate the conditions of the experiment by individuals 

 occasionally flying over from one area to the other. I regret I have intermingled in 

 my collection specimens of several other species of Shetland Geodephaga with British- 

 caught specimens, as nearly all the Geodephaga from those islands exhibited charac- 

 teristic differences in the shape of the thorax, or of some other portion of the structure, 

 distinguishing them at once from mainland specimens, and affording characters suffi- 

 ciently definite for a manufacturer of species to found new specific names upon. To 

 the naturalist who busies himself with nomenclature there appears to arise a great 

 practical difficulty from the disbelief in the permanency of species; but does not also 

 the naturalist who has full faith in the lastingness of specific forms, spend much of 

 his time in trying to ascertain which forms are properly designated as species and 

 which as varieties merely ? I am inclined to think, when once the fixity of species has 

 ceased to be a matter of faith, as it certainly will do sooner or later, principles of 

 nomenclature will be framed that will sweep away that dreadful incubus of synonyms 

 under which we now labour. 



" Let us try to answer the following question on this subject, Ought the North- 

 American and the European analogues of each other to bear the same or different 

 names? Where a difference of form exists between the individuals inhabiting the 

 two extreme geographical points of a large area, as when a North British form can 

 readily be separated from a South British one, ought the extreme and all the inter- 



