ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
751 
latter can be easily removed. After removal, the blastoderm was gene- 
rally left in a relatively large quantity of the preserving fluid for some 
hours longer. 
When the embryo was very much advanced, and the allantois had 
spread itself entirely beneath the shell, the removal of the shell was 
found to be a matter of some difficulty, as it is leathery and not brittle. 
The author says that he carefully scrapes the shell at one small spot 
with a knife until it becomes quite thin ; picrosulphuric acid is applied 
to the spot, which is again scraped, and acid again applied. This pro- 
cess must be repeated, with great care, until enough of the shell is worn 
off to expose a very small patch of the allantoic surface. However 
small the opening may be, the acid is able to penetrate and harden the 
tissues for some space around it. The opening may then be with safety 
gradually enlarged, until at last the entire shell can be removed with- 
out injury to the membranes. 
Preserving Ostracoda.* — Dr. G. W. Muller finds that preservation 
in 70 per cent, alcohol is sufficient for the examination of the shells and 
appendages of Ostracoda. With some, especially the Halocrypidse, 
the shell is too soft for this method, and it is well to place such in 
Canada balsam, to preserve the form of the shell. 
Preservation for histological purposes presents some difficulties, as 
the highly calcified shell is an obstacle to the entrance of the preserva- 
tive fluid. The best results were obtained with a mixture of 5 parts 
ether and 1 part absolute alcohol, from which, after a minute, the 
specimens were removed to 70 per cent, spirit. Useful preparations 
may be made by destroying the shell of living animals, and placing 
them quickly in 70 per cent, alcohol. 
Study of Mitosis. j" — In his study of the variations of mitosis in 
Ascaris megalocepJiala M. Y. Heda found that Prof. Van Beneden’s 
method was the best for fixing the eggs ; he used, that is, a mixture of 
1 part glacial acetic acid with 5 parts of absolute alcohol ; this mixture 
kills rapidly, while the achromatic elements remain very distinct. The 
best staining reagent appears to be vesuvin 0 * 25, malachite-green 0 * 25, 
distilled water 100, and glycerin 10 parts. The eggs, on removal from 
the fixing reagent, are at once placed in a drop of the staining fluid on a 
slide, and in this they are moved about. The preparation is then placed 
in a damp chamber for a day ; a cover-glass is then put on, and at each 
of its four sides a drop of glycerin (with 1/3 water) is allowed to fall. 
If, on examination, the preparation appears worthy of a detailed study, 
it must be decolorized. This is done by putting a drop of aqueous 
solution of glycerin at one edge of the cover-glass, and drawing it 
through till there are only traces of the stain. The solution of glycerin 
should be 10 per cent, if the preparation has just been stained, 30 per 
cent, if it was stained a short time previously, and 50 per cent, if the 
preparation is old ; this last solution may be employed for eggs set up 
some years since. It is well to have the worms as fresh as possible. 
* Fauna u. Flora des Golfes von Neapel, xxi. Ostracoda (1891) pp. 8 and 9. 
t Arch, de Biol., xiii. (“ 1893”) [1894] pp. 424 and 5. 
