1880.] Progress in Microscopical Science . i6g 
the structures to the best advantage ; indeed many of them 
are utterly useless. The subject is treated of under the 
heads of “ Material — Methods of Preserving and Hardening 
it,” “ Cutting of the Sections,” “ Tingeing Agents,” 
“ Method of Staining.” The paper is valuable on account 
of the large number of formulae given, and the numerous 
practical hints upon points where the experimenter is likely 
to meet with difficulties or take the wrong way of operating. 
The whole concludes with the following summary 
“ i. Let the material be quite fresh. 
2 a. Take care that the hardening or softening fluid is 
not too strong. 
b. Use a large bulk of fluid in proportion to the ma- 
terial. 
c. Change the fluid frequently. 
d. If freezing be employed take care that the specimen 
is thoroughly frozen. 
3 a. Always use a sharp razor. 
b. Take it with one diagonal sweep through the ma- 
terial. 
c . Make the sections as thin as possible, and — 
d. Remove each one as soon as cut, for if the sections 
accumulate on the knife or razor they are sure to 
get torn. 
4 a. Do not be in a hurry to stain, but— 
b. Remember that a weak colouring solution permeates 
the section better, and produces the best results ; 
and— 
c . That the thinner the section is the better it will take 
the stains. 
5 a. Always use glass slips and covers free from scratches 
and bubbles, and chemically clean. 
b. Never use any but extra thin circular covers, so that 
the specimens may be used with high powers. 
c. Always use cold preservatives, except in the case of 
glycerine jelly, and never use warmth to hasten 
the drying of balsam or dammars, but run a ring 
of cement round the cover. 
6. Label the specimens correCtly, and keep them on 
the flat and in the dark.” 
Herr Zeiss, of Jena, has produced a new low-power ob- 
jective, which, by altering the distance of its combinations 
by means of a rotating collar, gives a range of magnifying 
