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XXVII. On the Anatomy and Affinities of Pteronarcys regalis, Newm. : with 

 a Postscript, containing Descriptions of some American Perlidee, together 

 with Notes on their Habits. By George Newport, Esq., F.R.S., F.L.S. 

 Sfc. 8fc. 



Read May 2nd, and June 20th, 1848. 



1 HE existence of a winged insect which retains the branchial form of the 

 respiratory organs of its larva state as a permanent structure, was looked upon 

 by naturalists, when first announced *, as so curious a condition of life, that 

 many doubted its reality. Indeed, when I first observed branchiae in a speci- 

 men of Pteronarcys regalis (Tab. XXI. fig. 1), preserved in spirit, and brought 

 to this country by George Barnston, Esq., from Canada, I was fain to regard 

 them merely as of accidental occurrence, the result of incomplete development, 

 similar to what is sometimes observed in the partial retention of branchiae in 

 adult Amphibia, an example of which has lately been shown to me in a Triton 

 from Tunis. I was then disposed to think that the Pteronarcys, like this 

 Triton, had not completed its changes ; and, consequently, had retained in 

 its imago form a structure which it possesses as a normal organ in its inferior 

 condition as an aquatic larva, or pupa (fig. 2). But on minute examination, 

 other parts of its body were found to be of a perfectly natural type, a fact 

 which was strongly opposed to this view, since a well-marked aberration of 

 form, or I'etardation of development in one part of a body rarely or never 

 occurs without some alteration in another. 



On comparing this specimen with others preserved in a dried state, and now 

 in the cabinets of the British Museum, but which originally belonged to the 

 Entomological Club, and are the type specimens from which Mr. Newman 

 described his species, I immediately found that the retained branchiae were not 

 peculiar to the insect in my possession ; as branchiae, more or less developed, 



* Meeting of Entomological Society, December 4, 1843, and Annals and Magazine of Natural 

 History, January 1, 1844, p. 21. 



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