1889.] Microscopy. 
When the desired grade of staining is reai 
washed in alcohol, and mounted in Canada bals 
Still finer results may be obtained if the se< 
time in the stain, are placed in a saturate s 
lithium carbonate, for twenty-four hours. 
The following method will give quite the san 
A Simple Method for Removing the Gelatinous Layer 
from the Batrachian Egg.— Professor BlochmannS recommends 
the following as a quick and safe method for treating large masses of 
frog eggs : 
The spawn, having first been hardened in chrom-osmic-acetic acid, 
and then thoroughly washed in water, is placed in a beaker partly 
filled with dilute Eau de Tavelle (from three to four parts water), and 
gently agitated, that the fluid may reach all parts. In from fifteen to 
twenty minutes, according to the strength of the fluid, the glairy layer 
and the underlying membrane are dissolved, and the free eggs rest 
upon the bottom of the vessel. 
At this point special care must be taken lest the eggs become injured 
by striking each other. The fluid being poured off", the eggs are care- 
fully washed with water and placed through successive grades of 
alcohol. 
If the material thus prepared is not made use of at once it should 
be kept in a dark place to prevent the further withdrawing of the 
chromic acid. 
Eggs prepared in the above method stain nicely in borax carmine. 
This method of Blochmann's is the same as that recommended by 
Whitman in June, 1889 {vide this journal). 
The Differentiator Modified from report read before the 
British Association, September 11, 1889, at Newcastle, Eng. 
— According to the nature of the fluids in use, the differentiator takes one 
of the two forms here illustrated. As will be seen, a or a', the reservoir, 
b, the object-cylinder or object-box, and c, the filter, are three pieces 
of glass tubing joined together by means of caoutchouc tubing, the lat- 
. XII., No. 307, May, 1889, p. 269. 
