PRESIDKNT S ADi^KKSS. XIX 



Eveiy worker with the microscope has doubtless felt that 

 the inherent defect of this instrument is that wlien high powers 

 ai*e used which will reader the most minute and delicate 

 features manifest the greater portion is necessarily out of focus, 

 svhilst if a low power is used in which this defect is much less 

 obvious the details, which are of the greatest intei-est to the 

 observer, are lost sight of. The obvious suggestion is, that the 

 objects should invariably be placed in the thinnest possible 

 space so as to offer the least needful obstruction to the object- 

 glass on the one hand, and the light on the other ; and perhaps, 

 for many things, no apparatus is more simple and effective than 

 the Wenhara compressorium, which I liave very constantly 

 used. 



My desire has ever been not only to see the beauties of 

 microscopic life myself, but, so far as possible, to devise means 

 of showing them to others, or of helping those who need assist- 

 ance to see them and display them for themselves. 



Perhaps I have made more experiments with that charming 

 organism Yolvox (/[abator than with anything else, and the 

 mention of some may be of value to others. 



I directed my first attention to what may be'called massing 

 or crowding them together, getting them out of dirty into clean 

 water, freeing them from other things which it was undesirable 

 to show at the same time, and several methods succeeded very 

 well. 



Let us suppose that we have a jar with a good gathering 

 of Yolvox, and we wish to get them so thickly together that 

 the whole field of the microscope may be filled with them, 

 nothing being more beautiful as an object of display. The 

 most natural way to attain this is by filtering them out, and for 

 this purpose I have made some small metallic sieves, the mesh 

 of which is not more than one-hundredth of an inch in breadth, 

 such as the one I now have before me. This I place in a small 

 shallow vessel, pouring the water not through, but outside the 

 sieve, and then by means of a small syringe withdraw the 

 water through this fine gauze, continuing the process until I 



