384 SUMMARY OF CURRENT RESEARCHES RELATING TO 
process for one day in each solution was attended with good results. 
Thereafter the brain was placed for an hour in absolute alcohol, and 
cut in celloidin. 
Minute Structure of Electric Organ in Torpedo.* — Herr N. Iwan- 
zoff tried over a score of different fixatives, &c., but his best results were 
obtained when he used chromic salts — especially bichromate of potash — 
after injection with osmic acid, and stained with aqueous solution of 
haematoxylin. Osmic acid and Flemming’s fluid alone, or these with 
subsequent use of potassium-gold-chloride, were employed when staining 
was not desired. His paper includes a long discussion of various 
methods used by Fritsch and others. 
Differentiation of Hypodermic Glands.f — M. E. G. Racovitza de- 
scribes a means of differentiating hypodermic glands in Annelids 
( Micronereis variegata), when one wishes to study the order of appear- 
ance, number, or distribution, without investigating minute structure. 
The Annelid is placed gently in water on a slide, flooded with 
acetic acid, washed in distilled water for a few seconds, and then placed 
in mixture A, viz. : — Solution of methyl-green (Grubler) 0 # 3 per cent., 
1 vol. ; fluid of Ripart and Petit, 1 vol. The latter consists of chloride 
of copper 0*3 grm., acetate of copper 0‘ 3 grm., crystallised acetic acid 
1 grm., camphorated water, not saturated, 75 grm., distilled water 75 grm. 
The Annelid is coloured uniformly green in a few minutes ; but after 
3-6 days the body generally is decolorised, while the glands are 
intense blue. 
Then the specimens are placed in mixture B, viz. : — Pure glycerin, 
1 vol. ; fluid of Ripart and Petit, 1 vol. Thereafter the body is clear as 
crystal, except the glands, which are intensely blue. 
(5) Mounting-, including- Slides, Preservative Fluids, &c. 
Formol as a Preserving Fluid. J — Mr. F. C. Kenyon has an interest- 
ing essay on this subject. The first half of it is a free translation of a 
paper by Prof. T. Blum.§ It has been found that the properties of 
formol as a preservative medium may be summed up as follows : — - 
Animal objects are hardened without shrinking, and without losing their 
microscopic structure or staining properties; the natural form and 
colour is preserved ; the eyes remain much clearer than in alcohol ; the 
mucus of slime-producing animals is not coagulated and remains trans- 
parent ; the colouring matter of blood in tissues apparently disappears, 
but may be quickly restored by a high per cent, alcohol; plant structures 
are more or less well preserved ; most fruits keep well ; chlorophyll is 
not extracted, but after a long action of the fluid delicate leaves may be 
changed ; other colouring matters are retained for varying periods with 
individual plants ; microscopic sections of plants that have been a long 
time in formol give fine preparations. Dilute formol is incombustible, 
and is much cheaper than alcohol. To the results of Blum the author 
adds some experiments of other German naturalists and some notes of 
his own. He obtained some startling effects with salamander blood. 
* Bull. Soc. Imp. Nat. Moscou, 1895, pp. 407-89 (3 pis.). 
t Arch. Zool. Exper., ii. (1894) No. 3, pp. viii-x. 
% Amer. Natural., xxix. (1895) pp. 82-91. 
§ Ber. Senck. Naturf. Gesell. Franlif. a. M., 1894, pp. 195. 
