804 



SUMMARY OF CURRENT RESEARCHES RELATINQ TO 



head which clanips it if required, or releases it when needed for more 

 easy cleaning. Varying pressures of the cover-glasses are obtained by 

 turning the milled head in the centre of the plate as in Wcnham's com- 

 pressorium. The socket fits in a hole in the stage, in the same way as 

 stage forceps. 



Beaumont's Reservoir Life-slide. — Mr. C. E. Beaumont describes 

 this (figs. 146 and 147) as follows :— " Having long felt that if a cell were 

 constructed in which minute organisms could be kept alive under as nearly 

 as possible natural conditions, and at the same time allow of fairly high 



Fig. 14G. 



powers being used for their examination, a much more accurate knowledge 

 of the life-history of such organisms would be obtained, I at last con- 

 ceived the idea of making a slide having reservoirs at each end, in which 

 could be stored a supply of water ; and so made that a small current 

 could be continually kept flowing through the cell, from one reservoir to 

 the other, either on or oft" the Microscope, thereby keeping the organ- 

 isms in the cell constantly supplied with fresh water, in a manner as near 

 as could be similar to the conditions obtained in their natural habitat. 



Fig. 147. 



:5fc_L 



^^t 



The gentle percolation of water through the life-cell serves the treble 

 purposes of keeping the organisms cool, and supplying them with food 

 and aeration. It is not necessary to remind experienced microscopists 

 that when small organisms are placed with a drop of water in a shallow 

 cell and subjected to the concentrated light and heat from a condenser 

 during protracted observations with the Microscope, very great changes 

 are induced in the environment of the organisms, which very frequently 

 lead to important physiological changes. Assuming these changes to be 

 mainly caused by the concentrated heat from the condenser on so small 

 a quantity of water, the immense advantage of using a slide wherein 



