1901] MICROSCOPICAL JOURNAL. 195 
tube, and, if satisfactory, can be mounted in the usual 
way. Camphor, arsenic, and many others will suggest 
themselves as suitable for preparing slides in this way. 
The three methods described will practically cover the 
whole ground of preparing crystals for the microscope, 
and with the expenditure of a little time and patience will 
enable anyone to materially increase, at a nominal cost, 
his collection of slides. If mounted ina suitable medium, 
and preserved from undue heat and light, these slides 
will be permanent ; any change which may take place in 
the forms of the crystals may be put down to the solvent 
action on them of an unsuitable medium.—Pharmaceutical 
Journal. 
Notes on Microscopy. 
F. SHILLINGTON SCALES, F.R.M.S. 
STRIDULATING ORGANS IN BEETLES.—C. J. Gahan in 
“Trans. Entom. Soc.” London, 1900, pp. 433-52, com- 
ments upon Schrodte’s discovery of well-developed strid- 
ulating organs in the larve of several genera of beetles, 
and on the fact that the structures are generally alike in 
both sexes of adults, though with some notable excep- 
tions. He describes the stridulating organs on the head, 
on the prothorax and front legs, on the mesothorax and 
middle legs, and on the hind legs, elytra, and abdomen. 
ROTATORIA OF THE UNITED STATES.—In the “U.S. Fish 
Commission Bulletin” for 1899, pp. 67-104, are give all 
species of rotifers , 246 in number, hitherto found in the 
United States, with special reference to those discovered 
by the author in the great lakes. Two species Notops 
pelagicus and Pleurotrocha parasitica, are described as 
new. Asa general result of his investigation the author 
formulates the conclusion that the Rotatoria are practi- 
cally cosmopolitan, any species occurring wherever the 
conditions necessary to its existence are to be found. In 
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