1885.] Entomology. 507 
the other gives no twist to the plane of polarization, and so 
remains invisible; but by rotating the stage plate the latter 
muscle shines out brightly as the former retires into darkness. 
Mr. Cheshire finds this method of studying muscular layers in in- 
third object. These spermatozoa, about 200” in length, are ex- 
LIFE-HISTORIES OF Mıres.—At a late meeting of the Royal 
Microscopical Society, Mr. A. D. Michael read a paper “ On the 
Life-histories of some little-known Tyroglyphide.” In 1873 
Michael has found the acarus in England under the bark of 
reeds, destroying the reeds, not feeding on any insect, and con- 
cludes that it is probably a feeder on various kinds of bark, not 
on animal life. He has traced the whole life history. The male 
(previously unknown) presents the exceptional features possessed 
by the male of Tyroglyphus carpio, discovered by Kramer in 1881, 
and the hypopial nymph has been figured by Canestrini and Fan- 
zago in 1877 under the name of “parasite of an Oribata,” but 
without explanation. Mr. Michael finds in the life history of this 
