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XV. Notes on the Ephemeridfe, by Dr. H. A. Hagen; 
compiled {xoith remarks) hy the Rev. A. E. Eaton, 
M.A. 
[Read 5th May, 1873.] 
[Towards the middle of June, 1871, I received fi-om 
Dr. Plagen, of Cambridge, Massachusetts, a series of 
letters relating to the Ephemeridce. Thej contained much 
interesting matter, not only in the form of original obser- 
vations, but also in the shape of criticisms and corrections 
of my Monograph on the EphemeridcB, Part I., which had 
been published at the end of the preceding March. They 
conveyed information also respecting works which I had 
not been able to collate. 
The letters from which the notes subjoined are compiled 
are four or five in number. They consist, in a large mea- 
sure, of transcripts from Dr. Hagen's note-book, and the 
writing of each of them was a day's work. From this 
some idea may be formed of their extent. They are of 
a strictly private character. Written off-hand, in haste, 
without revision by the author, and with no intention that 
they should be published, they were susceptible of some 
little condensation, but not of much. The conjecture of 
one day was sometimes verified in a subsequent letter, so 
that remarks bearing on the same insect are to be found in 
more than one place. These scattered remarks it was 
advisable to bring together, so as to place the writer's 
views before the reader in the most convenient form. In 
order further to facilitate the application to my Monograph 
of the criticisms in the letters, I have reduced their mate- 
rials into an order corresponding in arrangement with my 
work, and have indicated the pages of the Monograph, in 
which will be found the passages touched upon in the 
Notes. 
My own remarks are enclosed in vincula [ ]. Amongst 
them I have introduced corrections of errors of printing 
in the Monograph, which were not discovered in time to 
be inserted with the other corrigenda in the Transactions 
for 1871.— A. E. Eaton.] 
TRANS. ENT. SOC. 1873. — PART III. (AUG.) 
