ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 425 



&. Collecting', Mounting' and Examining Objects, &c. 



Colouring Living Microscopical Organisms.* — A. Certes points 

 out that distilled and ordinary fresh water are toxic to marine In- 

 fusoria, and a great number of species whicli live in water of very 

 different density and chemical composition. 



In these special cases the colouring of living Infusoria will not 

 succeed, or only very imperfectly, unless care is taken to use a 

 solution of the colouring material prepared with the water which it 

 is desired to examine. 



The difficulties attendant upon the above procedure may be 

 avoided by the following process, which has also the advantage that 

 no foreign organisms are introduced. Place on the slide a drop of 

 the alcoholic solution (1:1000) of the reagent, cyanine, BBBBB 

 violet, gentian violet, dahlia, Bismarck brown, &c. Spread out the 

 liquid with a glass rod and let it evaporate. When the evaporation is 

 complete, or nearly complete, add a drop of the water (fresh or salt) 

 intended to be studied and put on the cover-glass. Almost imme- 

 diately, if the dose has been well calculatei, the phenomena of 

 paralysis and of colouring of the Infusoria may be observed. 



In this way the author has coloured several species of Vorticellce, 

 Paramecia, Amoebce, Polytoma uvella (flagellate) and Bacteria. 



Mounting Histological Preparations with Carbolic Acid and 

 Balsam."!" — Mr. G. E. Fell transfers the prepared sections from the 

 alcoholic preservative fluid to a clean slip and pours strong carbolic acid 

 over the object immediately, allowing it to run off at one corner of the 

 slide into a suitable receptacle. A thin cover-glass previously prepared 

 with Canada balsam is then quickly applied, the balsam replacing the 

 carbolic acid which, owing to its short contact with the tissue of the 

 preparation, does not produce in it any appreciable shrinkage while 

 still acting as a clearing agent. Pouring the alcohol over the pre- 

 paration on the slide (followed by the carbolic acid) and allowing 

 it to run off again, removes the extraneous filaments, bits of dust, &c., 

 from about the specimen. 



Dr. E. G. Mohr| considers, however, that it is scarcely worth 

 while to experiment with carbolic acid for histological mounts, as 

 Seller's method of mounting in alcohol balsam is so simple and 

 perfect as to leave nothing more to be desired. 



Differentiating Motor and Sensory Nerves.§ — By the method 

 adopted by L. Lowe and entitled " Method for obtaining preparations 

 which demonstrate the structural difference between motor and sensory 

 nerves, and are hence adapted for enabling the course of the fibres 

 of the peripheral system of nerves to be traced," a foetal rabbit, 

 3 to 4 centimetres in length, taken from the mother during life, 



* Sep. repr. Bull. Soc. Zool. France, vl. (1881). See the author's previous 

 papers, ante, pp. 279 aud 280. 



t Proc. Amer. Soc. Micr., 1881, u 87. 

 X Ibid., p. 88. 



§ Zool. Anzeiger, ill. (1880) p. 503. 

 Ser. 2.— Vol. II. 2 F 



