288 
and pith to hold the frozen tissue,-a small metal box 
about an inch by half an inch in area to hold the piece of 
tissue while freezing, are the necessary implements. The 
razor used for cutting the section must also be cooled 
in a bason full of snow, and the sections are most conve- 
niently cut in a room which is at or below the freezing tem- 
perature. It is convenient to have three razors in use, in 
order that the one used for cutting may be continually 
changed, since it rapidly gets warm, and begins to thaw the 
piece of frozen tissue. Very thin sections may be cut from 
frozen tissues, and immediately removed from the razor into 
the gold chloride solution, $ per cent. (or if so desired into 
silver nitrate). After remaining there from five to seven 
minutes, they should be removed to a vessel containing dis- 
tilled water and there allowed to soak for a fewhours. ‘They 
are then to be placed in water acidulated not with acetic but 
with lactic acid. Lactic acid, as pointed out to me by Dr. 
Kutschin at Leipzig, has a more rapid and certain action in 
reducing the gold chloride than has acetic acid. After the 
red-violet colour is fully developed, the sections may be 
teazed out or mounted whole in glycerine.—E. Ray Lan- 
KEsTER, Radcliffe Fellow. 
Dammar Varnish.—The following formula, for which we are 
indebted to Dr. Klein, will be useful to those who wish to 
try this medium :—Dissolve 1 oz. of gum Dammar in one 
fluid ounce of turpentine. Dissolve 1 oz. of Mastic in two 
fluid ounces of chloroform. Filter both liquids and mix. 
Mobility of Spines on Certain Insects’ Eggs. By H. 
Davis, F.R.M.S. (Communicated by Mr. Curties, August 
26th, 1870.) Thefollowing communication from Mr. Davis, 
addressed to Mr. Curties, was read by that gentleman:— 
Encouraged by your opinion that my observation of the 
mobility of spines on certain insects’ eggs would be a suitable 
offering to the Quekett Club, I venture to send some brief 
notes thereon, a few objects and illustrative drawings for exhi- 
bition at the meeting, and a parcel of photographs for distri- 
bution among the members. The discovery, such as it is, is a 
simple matter, and lies in a nutshell, or rather in an eggshell. 
You know that the eggs of some bird parasites have lately 
attracted much attention from theirnovelty and peculiar beauty ; 
foremost among them, the eggs found on the black-quilled 
Peacock, and on the Mallee bird: now the elegantly curved 
petaloid spines on the former quickly uncurl, straighten, and 
contract on the lid when the egg is placed under water. They 
remain thus close until the water is removed, when, as the 
egg becomes dry by evaporation, the spines loosen; they 
