ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 1075 



must be boiled in liquor potassre. When the axis of the skeleton is 

 left bare the detached and clean spicula are to be poured off into a 

 large test-tube and washed over and over again in distilled water until 

 all debris is got rid of; they are then to be dried and put into perfectly 

 clean dry bottles. A thin glass cover is to be cleaned, and a solu- 

 tion of 12 to 15 drops of strong gum-water in 1 oz. of distilled water 

 (filtered) is to be prepared, and a drop of this spread carefully over 

 the cover and allowed to dry (not dried by heat), put away under a 

 glass shade, or in a case impervious to dust. When the gum solution 

 is dry it is to be breathed upon until the surface is quite moist, and a 

 piece of fine muslin, which will just allow the spicula to pass 

 through its texture, being strained lightly over the neck of the 

 bottle the spicula are to be scattered evenly (as from a pepper- 

 castor) over the adhesive surface ; after a minute the cover is to be 

 taken up by means of forceps and tajrped upon a sheet of paper until 

 all non-adherent spicula are shaken off, when balsam is to be 

 applied. 



" Dry " mounts of spicula may, of course, be made in the same 

 way ; the cover, with the spicula attached to it, being secured to the 

 bottom of the cell. The advantage of this method is that the spicula 

 are firmly attached to the cover, aud all lie upon one plane. 



Preparation of Anthozoa.*— Prof. M. Braun has made some 

 experiments on Alcyonium palmatum, Caryophyllia cyatlms, and other 

 Anthozoa ; he treats them with a concentrated solution of corrosive 

 sublimate in sea-water, which he boils, and to which he then adds four 

 or five drops of a 1 per cent, solution of osmic acid to 20-25 ccm. of 

 the solution ; this is suddenly poured over the Anthozoa. After five 

 minutes the fluid is drawn off, and the specimens washed with sea- 

 water, and then gradually treated with alcohol, beginning with 30 

 per cent., and ending with alcohol of 96 per cent, solution. Hydra, 

 rotifers, and Polyzoa may be treated in the same way, and then pre- 

 served in Canada balsam, or be imbedded in paraffin and cut into 

 sections ; the preservation of the tissues will be found to be perfect. 



Prevention of browning in Plant Preparations.! — Dr. H. de 

 Vries finds that the browning of vegetable preparations depends on the 

 reduction of certain colourless substances (chromogens) by the oxygen 

 of the air. In order to prevent the appearance of this brown staining 

 the air and chromogenous substances are removed, the former in 

 boiling alcohol, the latter by extraction in acidified solutions 

 of spirit in water. The latter solution is preferable for most leaves 

 and stalks, the former for thin delicate leaves and for flowering parts. 

 The acids used are sulphuric or hydrochloric in 2 per cent, solution, 

 and the treatment lasts for some hours to several days. 



To remove the brown stain from vegetable preparations the author 

 employed the following solution: — 100 ccm. spirit, 0-2-0*5 strong 



* Zool. Anzeig., ix. (1886) pp. 458-9. 



t Maandbl. voor Natuurwetonscli., 188G, No. 1 (7 pp.). Cf. Zeitschr. f. Wiss. 

 Mikr., iii. (1S8G) pp. 280-1. 



4 A 2 



