The Miceoscope, 327 



is taken, not to put too much into each one: keep the various collec- 

 tions separate, and on reaching home remove them to shallow dishes, 

 exposing much surface to light and air. 



The above mentioned tools, together with a growing experience 

 and a firm determination, will enable one to capture Infusoria in 

 variety and abundance. The next question is how shall one proceed 

 to study them ? My answer must be very partial and unsatisfactory. 

 Here it is that technical skill, trained eyes and muscles, and refined 

 methods come in; these are acquired only by painstaking work, not 

 by reading what some one has done and how, nor by seeing some one 

 do work can the necessary touch of the learned be acquired ; the 

 student must work and be patient and hopeful. I shall, therefore, 

 only attempt to offer a few hints to beginners, hoping they may 

 assist some in gaining that experience which brings skill and the 

 pleasure of successful investigation; when the need of better tech- 

 nique is felt it will be found out and acquired. First of all, a good 

 microscope is necessary, supplied with at least the following objec- 

 tives and a full set of eye-pieces: a good inch, a long working- 

 distance quarter for searching, a first-grade quarter or fifth, and a 

 homogeneous eighth or tenth of widest angle, and most perfect con- 

 struction attainable. A dissecting-microscope of some form will be 

 found a great aid, while a camera, compressoriums, pipettes, needles, 

 scissors, pocket lenses, etc., can scarcely be considered less essential 

 than the microscope. I cannot too strongly urge the student to use 

 re-agents, and so far as possible make out the reason for the use of 

 each, and why it gives such results as it does. The most useful of 

 these are not many and are simple. Of these, osmic acid requires 

 the greatest care, but it is very useful in fixing Infusoria with 

 their bodies expanded. This may be done by isolating them in a drop 

 of water and carefully inverting the slip over the open bottle con- 

 taining the standard solution of the acid. A weak solution of iodine 

 in potassium-iodide is useful in the same way, besides those species 

 which move so rapidly and incessantly that it is impossible to more 

 than glimpse their parts and structure may be quieted by this 

 fluid without materially changing their forms; moreover, it is an ex- 

 cellent fluid in which to mount and permanently preserve these frail 

 specks. A highly dilute solution of tannin in glycerine is useful in 

 demonstrating the cilia, and also in causing the protrusion of the 

 trichocysts. Acetic acid, caustic potassa, carmine in a fine state of 

 division in water, and various staining solutions are each useful for 



