1. Add to a saturated solution of picric acid in water a strong solution of carmine in ammonia to saturation. 2. Evaporate the mixture to one-fifth its bulk over a water bath, allow it to cool, filter from deposit, and evaporate to dryness, when picro-carmine is left as a crystalline powder of red-ochre colour. Sections can be stained in a one per cent. aqueous solution, requiring only ten minutes for the process; wash well in distilled water, and transfer them to methylated alcohol, then to absolute alcohol, after which they are rendered transparent by immersing in oil of cloves or benzole, before mounting in balsam or dammar. To summarise Mr. Groves’ recommendations:-- 1. Let the material be quite fresh. 2. (_a_) Take care that the hardening or softening fluid is not too strong. (_b_) Use a large bulk of fluid in proportion to the material. (_c_) Change the fluid frequently. (_d_) If freezing be employed, take care that the specimen is thoroughly frozen. 3. (_a_) Always use a sharp razor. (_b_) Take it with one diagonal sweep through the material. (_c_) Make the sections as thin as possible; and (_d_) Remove each one as soon as cut, for if sections accumulate on the knife or razor they are sure to get torn. 4. (_a_) Do not be in a hurry to stain, but (_b_) Remember that a weak colouring solution permeates the section better, and produces the best results; and (_c_) That the thinner the section the better it will take the stains. 5. (_a_) Always use glass slips and covers free from scratches and bubbles, and chemically clean. (_b_) Never use any but extra thin circular covers, so that the specimens may be used with high powers. (_c_) Always use cold preservatives, except in the case of glycerine jelly, and never use warmth to hasten the drying of balsam or dammar, but run a ring of cement round the cover. 6. Label specimens correctly; keep them in a flat tray, and in the dark. Double and Treble Staining. Dr. W. Stirling[46] furnishes a brief but useful account of the methods he has employed with much success. _Osmic Acid and Picro-carmine._--Mix on a glass slide a drop of the blood of newt or frog and a drop of a one per cent. aqueous solution of osmic acid, and allow the slide to stand by. This will fix the corpuscles without altering their shape. At the end of five minutes remove any excess of acid with blotting-paper, add a drop of a solution of picro-carmine, and a trace of glycerine to prevent evaporation, and set aside for three or four hours to see that no overstaining takes place. At the end of this time the nucleus will be found to be stained red, and the perinuclear part yellow.