880 SUMMARY OF CURRENT RESEARCHES RELATING TO 



water containing any Tentaculifera fixes them most satisfactorily. Care 

 must be taken not to use too much, or they will become blackened and 

 useless. 



Entomostraca and small larva) can be fixed with bichloride of 

 mercury, and after being thoroughly washed, mounted in Noll's 

 medium. Salicylic vinegar (as above), 1 vol. ; dilute glycerin (glyce- 

 rin, 1 vol.; water, 4 vols.), 10 vols.; Farrant's medium, 11 vols. 

 This is generally a most useful fluid to keep by one, but does not 

 answer where the integument of the object is very chitinous. Vermes 

 are fixed admirably either by picric acid solution, or bichloride of 

 mercury, and Hydrse, by bichloride of mercury solution. Eydrachnse 

 may be splendidly preserved by putting them living into a cell con- 

 taining a saturated solution of boro-glyceride, and sealing the mount 

 down. The animal will probably live in this for a day or two, and 

 then will be perfectly preserved in form and colour ; while for Algre, 

 a few drops of saturated aqueous solution of salicylic acid added to 

 the water will preserve Volvox, showing cilia, and Spirogyra, without 

 contracting chlorophyll spirals, &c. Use very little of the solution, 

 otherwise it will bleach. 



Preserving Preparations of Algae.*— Dr. W. Migula, after alluding 

 to the difficulty of preserving good preparations of algae, e. g. Desini- 

 diaceae, on account of the plasma crumpling under the influence of 

 glycerin and acetate of potash, and also because the more complex 

 fluids destroy the chlorophyll, states that the contraction of the proto- 

 plasm may be perfectly prevented, if, so long as the algae are in pure 

 water, a drop of 1 per cent, osmic acid be placed on the edge of the 

 cover-glass. By this means the plasma is fixed without tissue change, 

 and after about 10 or 20 minutes the acetate of potash may be added. 

 Desmidiaceaa retain their form and the structure of the plasma 

 excellently. 



Removal of Siliceous Coverings from Fossil Diatoms, j— Dr 0. N. 

 Witt gives, by way of introduction, an account of the preparation of 

 material for microscopical research, which forms an important contri- 

 bution to the preparation-technique of fossil diatoms. 



Dilute hydrochloric acid is poured over bean-sized pieces of the 

 raw material, which is then heated in a water-bath. As there is but 

 little chalk or iron in solution, the adhesion of the particles is much 

 diminished, a condition favourable to further procedure. The acid 

 is then poured off and the residue washed with distilled water. It 

 is next heated with a 20 per cent, solution of carbonate of soda, in 

 which it is boiled for six or eight hours. The result is a fine soft 

 powder, which is again washed by decantation with distilled water. 

 The powder is then treated with strong hydrochloric acid whereby 

 fresh quantities of chalk and iron are dissolved. The author then 

 treated the material (after first washing out the hydrochloric acid) 

 with fuming nitric acid, to which had been added some chromate of 



* Zeitschr. f. Wiss. Mikr., iii. (188G) p. 47. 



t Sapiski Russischen Mineral. Gesell., xxii. (18S5). Cf. Zeitschr. f. Wiss. 

 Mikr., ii. (1885) pp. 573-5. 



