ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
753 
Staining. — Czokor’s cochineal-alum is the best all-round stain for 
embryos and embryonic areas, but Delafield’s hsematoxylin, borax- 
carmine, safranin, &c., are very clear nuclear stains. The author makes 
his alum-cochineal by mixing about 25 grm. of powdered cochineal 
and an equal quantity of powdered alum in about 800 grm. of distilled 
water and evaporating down to 600 grm. The mixture must be con- 
stantly stirred. A small piece of thymol is added to the solution in 
order to prevent fungi growing, and when cold the solution is filtered. 
It stains better when fresh, and is therefore the reverse in this respect 
of Delafield’s haematoxylin. According to size, the embryos remain in 
the stain for an hour to a day ; they are then washed in water as long 
as any colour comes out. Embryos which have been hardened in a 
solution containing platinum chloride should be stained as soon as 
possible (within a week), otherwise they stain badly or not at all. 
Before staining all the alcohol must be removed. 
Imbedding and Cutting . — Embryos are imbedded from chloroform or 
from bergamot oil. It is advisable to make the change from absolute 
alcohol to bergamot oil or chloroform a gradual one. The objects are 
first soaked in paraffin with a melting-point of 45°, and are then placed 
in paraffin of 56° melting-point heated in a water-bath to 80°-90°. It 
is of importance that all the chloroform or bergamot oil should have 
been driven off, otherwise the sections crumble. In dealing with fragile 
or brittle objects (e. g. lens, or if air has got into the preparation) it is 
advisable to brush over the surface of the paraffin block a layer of 
paraffin heated in a water-bath. By this device the section may be lifted 
off the knife with safety, and it does not curl itself up. 
Adhesion of Sections. — Schallibaum’s solution is used by the author 
for sticking the sections to the slide, and they are made to adhere firmly 
by treating them with the following mixture, which must be freshly 
made every four or five days : — new clear oil of cloves 3 parts and 2 parts 
of perfectly clear collodion. When stuck on with this mixture the 
sections adhere so firmly that they may be immersed in absolute alcohol 
for a whole day, and may be stained and decolorized as desired. 
This adhesion-method has the further advantage of allowing a series 
of sections to be examined a few minutes after they have been cut, for 
supposing no further after treatment is required, the paraffin is soon 
melted off over a Bunsen burner, and then the slide can be at once 
transferred to xylol. As a mounting medium the author uses xylol- 
dammar, and always warms the cover-glass before imposing it. 
Use of Stabilite for Celloidin Preparations.* — Herr O. Jelinek 
recommends the use of the new insulating material stabilite in preference 
to wood or cork on which to fasten the celloidin block. The disadvan- 
tage of the use of wood or cork for this purpose is that colouring matter 
and tannic acid are extracted from them by immersion in alcohol. In 
seeking for some material to replace them the author was guided by the 
following considerations. The substance must be perfectly insoluble in 
water and alcohol ; it must be possible to easily cut from it blocks of 
different size and shape with the knife or saw, and these blocks must be 
hard and not alter their shape by clamping ; the celloidin must adhere 
, * Zeitschr. f. wiss, Mikr., xi. (1894) pp. 237-42. 
