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plains below, and that they would be just as true Bryoniae as those of the present 

 — the result of the influence of climate on an impressionable organism, and the 

 power of that organism to accommodate itself to altered conditions. 



Now, then, let us return to our poor old friend Semidea, who has been having 

 such a weary time of it on top of Mount Washington, for the last eighty thousand 

 years. I do not know the form of Chionobas that flies on the plains of New 

 Hampshire. I am dealing with one of the laws of nature that controls life, a far 

 more reliable guide to correct conclusions, than the changeable external appear- 

 ance of insects. But whatever they may be like, or by whatever name they may 

 be called, I am quite confident, that upon investigation one of them will be 

 found to stand in the same relation to Semidea that Napi does to Bryoniae, and 

 will be found capable of pushing its way up Mount Washington and to be modi- 

 fied by the changed conditions, and by the time it has established itself on the 

 top it has become true Semidea; so that if at any time Semidea had been obliterated 

 from Mount Washington by the severity of the conditions, and it would seem 

 little short of a miracle if it never has been, its place could yet be filled from 

 below. 



Then there is Semidea in the Mountains of Colorado. The Chionobas of the 

 Colorado plains, will undoubtedly be diflerent-looking from those of New Hamp- 

 shire and discerned by bearing diflerent names, and from one of them the Semideas 

 have come which are found on the mountains ; the same principle governing 

 one as the other. We turn to Labrador and the same principle is at work there, 

 only the conditions for the production of Semidea are obtained without the neces- 

 sity for the elevation. So that from Labrador within the Arctic circle, to Long's 

 Peak, Colorado, an unbroken chain of that species extends across the 2,800 miles 

 that lie between, every link of which may difier somewhat from the one next 

 to it, according to the conditions in which it lives, and be entitled to a distin- 

 guishing name, yet all united by the laws of consanguinity. At these three points, 

 Labrador, Mount Washington and Long's Peak, Colorado, the conditions being the 

 same, like results are produced and Semidea is the natural outcome. And according 

 to Mr, Edwards, when specimens are brought from these widely separated locali- 

 ties and compared, they are not known to difler by a scale or a hair. I see that 

 Mr. Scudder does not consider the Labrador form quite the same as the others, 

 if so it would indicate that the conditions are not quite identical. 



Mr. Edwards inform us that the Satyrinae are a very numerous family, with 

 many genera, these having numerous species, which I take as an indication that 

 they are sensitive to external influences and readily modified thereby, and pro- 

 bably a full series might exhibit the gradations to be slight. 



This, then, is the view I take of the way in which Arctic forms have been 

 originated and perpetuated, and the principle at work in producing them is 

 that which has been so carefully elaborated with such a wealth of illustration 

 and knowledge of facts by Wallace in his Island Life ; only he calls the forms 

 produced by changed conditions " species " instead of varieties of a species, a 

 mode of using the terra that is ever liable to lead to confusion and misun- 

 derstanding. 



