252 THE MICROSCOPE. 



when immersed in dilute nitric, chromic or osmie 

 acids, but remains transparent, and is sufficiently indif- 

 ferent to reagents. A mass of similar properties is 

 made of glue liquid when cold, coloured with the 

 violet extract of logwood reduced with alum. Injec- 

 tion is effected in the case of worms (leech and earth- 

 worm) by way of the ventral or dorsal vessel, with 

 large Crustaceans by the heart or the ventral vessel 

 which lies in the sternal canal. In many cases, 

 especially when lacunar spaces have to be filJed, use- 

 ful preparations are obtained by natural injection 

 (auto-injection, or autoplerosia). Natural injection of 

 Medusa3 is effected without injuring the vessels ; in 

 the case of Crustaceans, Insects, and Mollusca, through 

 a slit with an opening at the side remote from it. 

 Medusa3 are laid in a glass vessel, with the bell down- 

 wards, and a bell- jar ending in a narrow tube above 

 is placed over it and made air-tight; after the Medusa 

 is covered with the injection-mass, the air in the glass 

 is exhausted, and as the sea- water runs out by slits 

 in the lower side of the annular canal, the coloured 

 fluid runs in. In the case of leeches and large 

 species of earthworms, the natural injection is made 

 from the ventral sinus. In all cases a glass tube is 

 nsed, with a finely drawn-out point. The injection 

 is complete when the injection issues from the counter- 

 opening. Animals to be injected alive are kept quiet 

 by cold (upon ice). Besides the animals mentioned, 

 large caterpillars, beetles, Libellulidse, Iarva3, locusts, 

 &c., all serve as objects for injection ; the glass can- 

 nula being introduced into the posterior end of the 

 dorsal vessel, and the counter-opening made in the 

 ventral vessel, and vice versa. 



Staining Living Protoplasm with Bismarck Drown. 

 L. !\ Henneguy having treated Paramoecium aurelia, 

 with an aqueous solution of aniline brown (known as 

 " Bismarck Brown "), found that they assumed an 

 intense yellow-brown colour. The colour first appears 

 in the vacuoles of the protoplasm, and then in the 

 protoplasm itself, the nucleus generally remaining 

 colourless, and thus becoming more visible than in the 



