*Barrett’s formula.*--Introduced by Dr. W. H. Barrett, of Belfast. It gives almost as good results as the above. It is made from ordinary English extract of logwood, and is considerably cheaper. The extract should be dried, and finely powdered, and then extracted with absolute alcohol for several days. Powdered extract of logwood 2 grms. 1-1/2 drms. Absolute alcohol 10 c.c. 1 oz. Filter and add slowly to Benzoate of sodium 1 grm. 36 grs. Alum 1 grm. 36 grs. Distilled water 100 c.c. 10 ozs. The strength of the solution will vary with different samples of logwood and must be estimated by trial. This solution is comparatively cheap and is useful for class purposes. *Ehrlich’s hæmatoxyline.*--This very useful nuclear stain is made as follows:-- (_a_) Hæmatoxyline 2 grms. 9 grs. Absolute alcohol 100 c.c. 2 ozs. (_b_) Glycerine 100 c.c. 2 ozs. Distilled water 100 c.c. 2 ozs. Alum 120 grms. 2-1/2 ozs. Glacial acetic acid 5 c.c. 24 mins. Add (_a_) slowly to (_b_) with constant agitation. Allow to ripen in sunlight for two months before using. It may be employed as a rapid stain undiluted but far better results are obtained by using a weak solution, a few drops to a watch-glass full of distilled water, and staining slowly for from half an hour to two hours. The solution improves by keeping. If after a time the staining becomes diffuse it is an indication that the acetic acid has evaporated, and a few drops more should be added. *Kleinenberg’s hæmatoxyline.*--This formula differs from the previous one in being an alcoholic solution. The calcium chloride is added because it “sets up diffusion currents between the alcohol in the material to be stained and the alcoholic staining solution, so enabling the latter to penetrate more rapidly” (Squire). It is much used in staining embryonic specimens in bulk before embedding in paraffin, and was strongly recommended for that purpose by Foster and Maitland Balfour. Various formulæ have been given from time to time. That advised by Squire (_Methods and Formulæ_, p. 25) can be accurately made up without much difficulty. (_a_) _Crystallised_ calcium chloride 20 grs. 1/2 oz. Distilled water 10 c.c. 2 drms. (_b_) Alum 3 grms. 32 grs. Distilled water 16 c.c. 170 mins. Mix and add Rectified spirit 240 c.c. 8 ozs. Allow it to stand and any excess of calcium sulphate, &c., to separate. Filter and add Hæmatoxyline 2-1/2 grms. 25 grs. A little thymol should be added as a preservative.