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XXVII. On the Anatomy and Affinities of Pteronarcys regalis, Newm.: with 
ù Postscript, containing Descriptions of some American Perlidæ, together 
with Notes on their Habits. By Grorce NewrorrT, Esq., F.R.S., F.L.S. 
&c. &c. he 
Read May 2nd, and June 90th, 1848. 
THE 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 branchie in a speci- 
men of Pteronarcys regalis (Tas. 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 branchiz 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 Pferonarcys, 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 retardation 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 branchiz were not 
- peculiar to the insect in my possession; as branchiz, 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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