ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
173 
tation. The decantation error is minimised by the shape of the funnel 
devised by Mr. Jackson. The amount of sand error depends on the 
character of the organisms, upon the size of the sand-grains, and the 
depth of the sand. The decantation error chiefly depends on manipu- 
lation, and arises from some of the organisms remaining attached to the 
sand-grains. 
C2) Preparing- Objects. 
Isolation of the Elements of the Crystalline Lens * — Dr. W. Geb- 
hardt places the eyeball in a 4 to 10 per cent, solution of formalin for 
one or two days. All the transparent parts retain their transparency, 
and the vitreous its muco-gelatinous consistence. The bulb, which may 
be preserved in the formalin solution, is then transferred to 50-60 per 
cent, alcohol for a couple of hours. The lens is then taken up and 
gently squeezed between two fingers. By slight pressure it is broken up 
into separate lamellae, which can be easily teased out in water or glycerin. 
Both the toothed and smooth fibres are easily isolated, the teeth being 
extremely clear. The preparation may be stained, and mounted in 
glycerin-gelatin. 
Method of Preparing Rotifers.j — M. N. de Zograf has a note on 
this subject, in which he states that, after trying Mr. C. F. Rousselet’s 
method of preserving rotifers, he found that formalin preserved the 
animals for a very short time only. To this it must be remarked that, 
while M. de Zograf’s experience cannot have extended for more than 
twelve months, in this country the rotifers mounted by Mr. Rousselet 
in formalin for the last three years have kept extremely well, and look 
at present as if they were going to keep a great number of years more. 
The only difficulty experienced has been to prevent the evaporation of 
the watery fluid, which has now apparently been overcome by using 
thickened gold size and Bell’s cement for sealing the slides. 
M. de Zograf mentions a method by which he has succeeded in 
mounting rotifers in balsam. After narcotisation with cocain, killing, 
and fixing with *25 per cent, osmic acid, a rather large quantity of a 
weak (10 per cent.) solution of raw wood vinegar is added, and the ani- 
mals left therein from five to ten minutes ; they are then washed in three 
changes of distilled water, which is gradually replaced by alcohol of 
progressive strengths, finishing with absolute alcohol. In this way the 
rotifers do not shrink, and can be passed into glycerin or Canada balsam 
in the usual way. The protoplasm and organs are coloured by this 
method a bluish-grey or deep black, but the histological structure is 
well shown. 
(3) Cutting, including Imbedding and Microtomes. 
New Microtomes by Fromme.J — Prof- J- Schaffer described two 
new microtomes, made by Fromme Brothers, of Vienna, for cutting large 
sections : — 
1. For Paraffin-Imbeddings . — The object is carried at the side of a 
rectangular frame, which is fixed to a horizontal axis working in bearings 
* Zeitschr. f. wiss. Mikr., xiii. (1896) pp. 306-7. 
t Comptes Rendus, cxxiv. (1897) pp. 245-6. 
% Zeitschr. f. wiss. Mikr., xiii. (1896) pp. 1-9 (3 figs.). 
