94 THE SEA SHORE 



the wax with two or three small pieces of lead pushed down into 

 it while it is yet soft. 



With such a dissecting microscope and trough as we have 

 described one may do a great deal of exceedingly useful work, 

 both hands being quite free to manipulate the object under 

 examination. 



The dissection may be conducted with the aid of a small scalpel 

 or other very sharp knife, the parts being arranged or adjusted by 

 means of a needle, mounted in a handle, and held in the left hand. 

 Sometimes, however, the object to be dissected is so minute that 

 even a small scalpel is too large for the purpose, and in such cases 

 nothing is better than little dissecting instruments made by mount- 

 ing large sewing needles in suitable handles, and then grinding 

 down the points of the needles on two opposite sides, on a hone, so 

 as to produce little pointed, two-edged blades. Bent needles are 

 often useful, too, and these may be prepared by heating the points 

 to redness in a gas-flame, bending them as desired while hot, and 

 then hardening them by suddenly thrusting them, 'at a red heat, 

 into cold water. 



The compound microscope will often prove useful for the 

 examination of very minute objects, as well as for the study of the 

 structure of the principal tissues of the larger species ; but since 

 detailed instructions for the management of the microscope, and 

 for the preparation of objects for microscopic examination would 

 occupy much more space than we can spare, we shall content our- 

 selves with nothing more than a few general hints on this portion 

 of the young naturalist's work, dealing more particularly with those 

 points which commonly present difficulties to the amateur. 



If it is desired to examine some minute living object, such as a 

 protozoon, place the object in a drop of the water in which it lived 

 just in the middle of a clean glass slip, and cover it with a cover- 

 glass. The quantity of water should be just sufficient to fill the 

 space between the two glasses. If less than this has been used, a 

 little more applied to the edge of the cover by means of a glass rod 

 will immediately ran in between the glasses ; while if an excessive 

 amount was employed, the surplus may be removed by the applica- 

 tion of a strip of blotting paper. Place the glass slip on the stage 

 of the microscope, and reflect light through it from the mirror 

 below. 



Examine it first with a low power ; and, after having observed 

 as much as possible of the creature's movements and structure with 



