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VI. — The Adion of Tannin on the Cilia of Infusoria, with 

 Bemarhs on the use of Solution of Sulphurous Oxide in 

 Alcohol. By Henry J. Waddington. 



{Read Uth March, 1883.) 



I AM desirous of bringing to the notice of the Society this eyening 

 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 Paramseoium 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 suspen- 

 sion by pieces of weed or Confervse, these crumbs, after a short 

 time, form a nucleus from which fungoid growths spring freely, 

 so that from a fragment of biscuit l-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 hfted out of 

 the water, the filaments necessarily collapse, and act as a net to 

 inclose whatever may be among them. When placed on a shp, 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 successfully 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 Anaeharis or filaments of Conferva, which 

 have been reduced to a pulp with a little water in a mortar. If 

 a few drops of this are occasionally added to the trough con- 

 taining the Infusoria, they may be kept satisfactorily for a length 

 of time. The small trough I have here to-nigh b has been so kept 

 for more than four months. 



In trying the effect of various chemicals on Infusoria — princi- 

 pally Paramecium Aurelia — I was led to use a solution of tannin, 

 or tannic acid ; and I was surprised to find that the immediate 

 action of this chemical was to render the ciHa visible without any 

 manipulation of the light. It may have been noticed that when 

 these Infusoria have been killed by ordinary means, such as heating 

 the water in which they are contained, the cilia are very difficult 



