

A DESCRIPTION OF THE ROUSSELET 

 COMPRESSORIUM. 



By Chas. F. Rousselet, F.R.M.S. 



(Bead January 20th, 1905.) 



Some misconception seems to have arisen about the small com- 

 pressorium which bears my name, and it will perhaps, therefore, 

 be advantageous to here set forth its special features and 

 advantages, more especially as no figure or description of it has 

 hitherto appeared in the Journal of the Qvekett Club. 



The idea of this compressorium forced itself upon me about 

 1890, owing to the great difficulty and loss of time I experienced 

 when examining small moving animals, such as Infusoria, Roti- 

 fera, etc., with high powers, under proper and critical illumina- 

 tion with modern condensers. The then existing compressors 

 were not satisfactory, and failed to produce the desired result. 

 My previously devised live-box,* though right in principle and 

 efficient for objects not too small, did not allow of a sufficiently 

 delicate and graduated movement and accurate control of the 

 compression. 



What I wanted was a small, handy compressorium which 

 would satisfy the following conditions : 



1. The securing with precision and holding of any small Eotifer 

 or Infusorian between the glass tablet and cover-glass, without 

 crushing or even hurting it. 



2. The possibility of examining the secured animal in any part 

 of the field, wherever it may have been caught between the two 

 glasses, with all powers, including water and oil immersion 

 lenses. 



3. The possibility of critically illuminating the animal from 

 below with modern wide-angled condensers. 



* For the special purpose of rendering it air-tight and preventing 

 the evaporation of the water on the slide, this live-box can very well be 

 modified and improved as suggested by Mr. Merlin (p. 1G9), and for the 

 continuous observation of organisms which do not admit of compression, 

 such as Monads and Bacteria, the live-box will probably answer better than 

 the compressorium. 



