ZOOLOGY AND BOTANY, MICROSCOPY. ETC. 469 



to prove its claims to superiority over all other stains yet tried. Not 

 only is the process more rapid than any hitherto used (except that of 

 Glorieux, and it equals even this remarkably rapid method), but a greater 

 number of bacilli are developed. I'urther than this, the bacilli appear 

 to be swollen by the process, and show up larger and more clearly. 



C5) mounting, including Slides, Preservative Fluids, &c. 



Preparing and Mounting Diatoms.* — In his account of the diatoms 

 of the Bay of Villafranca, M. Peragallo recommends the following plan 

 for separating and preparing them for examination, in the case of those 

 species which are dredged up from the bottom mixed with sand and mud. 



The material is first passed through a coarse sieve with meshes about 

 1 mm. in diameter, the residue (which has passed through the sieve) 

 placed in a dish, and hydrochloric acid added drop by drop to dissolve the 

 calcareous matter ; when effervescence has ceased, the deposit is placed 

 in a large vessel and allowed to settle repeatedly after washing with 

 water until every trace of acid has disappeared. It is then boiled in 

 water alkalized by potassium or sodium carbonate, and shaken; the 

 diatoms fall to the bottom, while the mud remains in suspension, and by 

 repeated decanting the diatoms are obtained with but small admixture 

 of any foreign matter except sand, especially if finally treated with 

 sulphuric acid. The diatoms are lastly separated from the sand by a 

 tedious process of moistening with alcohol and passing down an inclined 

 glass tube, when the diatoms pass down and the sand remains behind. 

 The whole process occupies more than a month, but is stated to produce 

 very good results. 



For mounting, the diatoms are always placed on the cover-glass. 

 The fixing material recommended is gum adraganth, as prepared by 

 M. Brun of Geneva, the refractive index of which is very near to that 

 of glass, and as a saturating fluid a solution of styrax or liquidambar in 

 benzin or in a mixtui-e of benzin and absolute alcohol. The diatoms 

 are placed in the position they are intended to occupy on the cover-glass 

 by means of a mounted hair or small pincers with a wooden handle. 

 The pincers are then lightly dipped into the solution of gum adraganth, 

 and, after moistening the cover by the breath, the diatoms are lightly 

 touched with the pincers. When the moisture has entirely evaporated, 

 a drop of the saturating fluid is placed on the cover-glass, and when the 

 air-bubbles have entirely disappeared, and before the fluid has completely 

 evaporated, a drop of styrax is added. The preparation is then warmed, 

 and placed by pincers on the slide, and the excess of styrax removed by 

 linen soaked in alcohol. 



Mounting Diatoms.! — M. Bialle de Langibaudiere mounts diatoms ia 

 the following manner. Upon a clean cover-glass, previously placed upon 

 a bronze or iron table, are dropped from a pipette several drops of 

 distilled water. Then from the bottle in which the diatoms aro 

 preserved in spirit, is removed a small quantity of the fluid, with the 

 same pipette. Of this fluid one drop is let fall into the distilled water 

 on the cover-glass. Owing to the alcoholic fluid falling into water, the 

 diatoms are scattered all over the cover-glass. The metal table is then 

 gently heated, so that the water evaporates very slowly and without ebul- 

 lition. The rest of the manipulation is performed in the usual manner. 



* Bull. Soc. Hist. Nat. Toulouse, xxii. (1888) pp. 16-35. Cf. ante, p. 427. 

 t Joum. dc Micrographie, xiil (1889) p, 59. 

 1889. K 



