142 THE MICROSCOPICAL NEWS. 
by the common fault of want of perfect flatness of the plane 
surface of the stand. F 
The beautiful adaptation of a sliding glass restricted by a point, 
whilst it relieves the microscopist from the expenditure involved 
by a complicated brass movement, is so easily fitted that there is 
no excuse for employing the fingers alone. 
THE ACTION OF TANNIM 
ON THE CILIA OF INFUSORIA, WITH REMARKS ON THE USE 
OF SOLUTION OF SULPHUROUS OXIDE IN ALCOHOL. 
By Henry J. WapDINGTON. 
(Extracted from the Journal of the Royal Microscopical Society. ) 
AM desirous of bringing to the notice of the Society a matter 
which, though small in itself, may be of some use in the 
hands of experts. The immediate subject is the peculiar action 
of tannic acid on the cilia of Paramecium aurelia ; but I may, 
perhaps, be allowed to digress a little at starting, in order that I 
may call attention to the methods I have used for keeping Infusoria 
for microscopical observation. 
There are two methods which I have found very useful for 
this purpose. If small fragments of very hard burnt biscuit are 
dropped into water containing Infusoria, and held in suspension 
by pieces of weed or Conferve, these crumbs, after a short time, 
form a nucleus from which fungoid growths spring freely, so that 
from a fragment of biscuit 1-32nd in. in diameter we may have a 
spherical growth of 3-4ths in. in diameter. These growths seem 
to be peculiarly fitted for the development of certain kinds of 
Infusoria, and they have this advantage—that when lifted out of 
the water, the filaments necessarily collapse, and act as a net to 
inclose whatever may be among them. When placed on a slip, a 
portion of these filaments may be spread out with needles, and 
they then serve the purpose of so retarding the motions of the 
Infusoria that their observation is comparatively easy, the extreme 
fineness of the filaments allowing the highest powers to be success- 
fully used. It is necessary that the biscuit should be very hard 
and well baked, otherwise the fragments disintegrate. This 
method applies to Infusoria in aquaria, or in comparatively large 
quantities of water ; but where they are contained in small troughs, 
I find that they thrive well on leaves of Axacharis or filaments of 
Conferva, which have been reduced to a pulp with a little water 
