290 THE NORTHERN MICROSCOPIST. 
of a perfect gill, Ephemerella has only the fourth to the seventh seg- 
ments furnished with gills, the smallest number amongst British 
genera. Coenis, with six single gills on each side, all well fringed, 
has those on the third segment large enough to cover the four 
hinder pairs, the second segment being without gills. 
Baetis and Centroptilum have seven single gills on each side; - 
Cloéon (Fig. 60.) has six double and the seventh single ; in these 
three genera they are oval and without fringe. Siphlurus has two 
double and five single gills on eachside, without fringe. Ephemera 
is often described as having only six pairs of double lance-shaped 
gills, all fringed. It has, however, another pair, very small and 
plain, on the first segment, sometimes concealed by the wing-cases. 
Minute branches of the tracheze run through the gills, and when 
these are fringed, each filament receives a single branch. 
(Zo be continued. ) 
NORTHERN SOCIETIES. 
BACUP Natura History Society. Hon. Sec. : Mr. George Calvert. 
BOLTON Microscorrcat Society. Hon. Sec.: Mr. W. Rideout. Meets on Friday 
evening once in each month. ; ; 
CHESTER Naturat Science Association. Hon. Sec. of Microscopical Section : 
Mr. J. D. Siddall. 
DONCASTER MicroscoricaLt Society. Hon. Sec.: Mr. M. H. Stiles. Meets 
twice in each month. 
HALIFAX. A Private Society. Members meet at each others houses. 
LEEDS. No Microscopical Society in existence. 
LINCOLN Scrence Crus. Hon. Sec. : The Rev. W. W. Fowler, M.A., F.L.S.. The 
School House, Lincoln. 
LIVERPOOL Microscorrcan Socrety. Hon. Sec.: Mr. I. C. Thompson. Meets 
First Friday in each month. 
MANCHESTER Microscoprcat Society. Hon: Sec.: Mr. C. L. Cooke. Meets 
First Thursday in each month. 
MANCHESTER Cryprocamic Society. Hon. Sec.: Mr. Thos. Rogers. Meets 
Third Monday in each month, at Old Town Hall, King Street. 
MANCHESTER SCIENCE AssoctaTION. Hon. Sec.: Mr. J. Percival Yates. Meeting 
Second and Fourth Tuesday in each month. 
NEWCASTLE-ON-TYNE. Norru or ENGLAND MicroscopicaL Society, Hon. 
Sec.: Mr. M. H. Robson. Meets Second Wednesday in each month. 
NOTTINGHAM Lirerary anp PuariLosopHicaL Society. Natural Science Section 
eee Fortnightly on Wednesdays. Hon. Sec.: Mr. A. H. Scott 
hite, 
OLDHAM Microscorrcat Socrery. Hon. Sec.: Mr. Charles Walters. Meets on the 
Third Thursday of each month, in the Club-room of the Lyceum. 
ROCHDALE AND WHITWORTH Mrcroscoricat Sociery. Hon. Sec., Mr. I. 
Renshaw, L.D.S.R.C.S. 
SHEFFIELD. Hon. Sec. , Mr. B. W. Wood, F.R.M. M 
Te ere oe ae 00 R.M.S. eets on the First and 
