ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 473 



is then to be mixed with the water in which the animal is swimming. 

 The narcotic may be cocain, of which a drop of 1 p.c. solution is usually 

 sufficient to numb and kill the animal in about 10 minutes. Chloral 

 hydrate £ to T V p.c. is also good, especially for Bryozoa. The best 

 narcotic is hydroxylaniin in r \- to £ p.c. aqueous solution. But as the 

 commercial article often contains hydrochloric acid, it is necessary to 

 neutralise carefully with soda before using. 



The animals are next to be fixed by means of the usual methods, 

 but if cocain has been used for narcotising, corrosive sublimate must 

 not be employed, as a copious precipitate forms ; and as hydroxylamin 

 has a strongly reducing action, easily reducing fixatives should be 

 avoided. Instead of ordinary fixatives graduated alcohols answer well. 

 If it be necessary to bleach the animal, peroxide of hydrogen in 1 p.c. 

 solution, much diluted eau de Javelle, or magnesium peroxide may 

 be used. 



The preparation should now be thoroughly washed, and is then 

 ready for staining. Mayer's paracarmin is very good for this purpose, 

 and it is prepared as follows : 1 grm. carminic acid, ^ grm. chloride of 

 aluminium, 4 grm. calcium chloride are dissolved in 100 c.cm. of warm 

 70 p.c. alcohol. The object to be stained should not have an alkaline 

 reaction, and should be washed with a weak solution of aluminium 

 chloride in alcohol. 



Nikiforow's neutral borax carmin is also serviceable. This consists 

 of 3 grm. carmin, 5 grm. borax, which are boiled in 100 c.cm. of water. 

 As much ammonia as will dissolve the carmin is then added, and the 

 mixture evaporated down to half its bulk. Dilute acetic acid is then 

 added until the cherry-red colour disappears. This solution should be 

 diluted when used. The preparation should then be dehydrated if it 

 is to be mounted in balsam. But a better medium is prepared as 

 follows : (1) Pyroxylic acid with a little salicylic acid diluted freely 

 with water and glycerin. (2) Ten parts of selected gum arabic are dis- 

 solved in 10 parts of water and 5 parts of glycerin, and a little camphor 

 is added. Equal parts of the two solutions are mixed together when 

 required. 



As a substitute for Canada balsam, Yosseler's turpentine mixture is 

 recommended. This is prepared by mixing equal bulks of Venetian 

 turpentine and 96 p.c. alcohol in a tall vessel, which is placed in some 

 warm situation. After 3 or 4 weeks the clear supernatant fluid is 

 decanted off. Mounted in this medium, the fine details of an object 

 -stand out excellently well. 



Fixing and Examining Cyrripida Larvse.* — H. Eossig, for his 

 researches on gall-formation, mostly used sublimate for fixing the larva?. 

 The solution employed was Petrunkewitsch's modification of Gilson's 

 formula. This was used hot for a few seconds, the larvae being after- 

 wards transferred to a cold solution. Flemming's and vom Bath's 

 fluid were also used, but the internal parts were often cloudy. 



After the larva? had remained in the sublimate for 2 to 12 hours, 

 they were washed in 70 p.c. alcohol to which iodine was added. The 



* Zool. Jahib, xx. (1901) pp. 28-0 (4 pis.)- 



