ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 1071 



Another useful method of preservation is to receive the fresh 

 semen on a slide, and spread out a thin layer by drawing another slide 

 through it, over the glass. This film is then set aside for ten 

 minutes, or until perfectly dry. A solution of eosin is then applied 

 and left on the slide five or ten minutes, after which the excess of 

 staining reagent is washed away by gentle agitation of the slide in 

 clean water. It is again allowed to dry perfectly. A. drop of 

 Canada balsam is then applied, and covered as usual. This is a very 

 simple method, and may advantageously be had resort to when it is 

 desired to photograph the spermatozoa, the red stain giving the 

 needed photographic opacity. But the cells are of course shrunken 

 and distorted by this method, and only their coarser features can be 

 preserved. 



Demonstrating the mucous secretion of the skin of the Trout 

 Embryo.* — Dr. L. Merk recommends for the study of the secretion 

 of goblet cells, the embryo of the brook trout in which the epithelium 

 on the body and on the yolk-sac is crowded with these forms. The 

 embryos are available from the time when the eye-points appear. The 

 smaller animals can be examined in water in a hollow ground slide, 

 but the author preferred to cut the yolk-sac and isolate the investing 

 membrane by waving it to and fro. The separation of the yolk-sac 

 was undertaken in 0*75 per cent, salt solution because the issuing 

 yolk is not precipitated therein, while in water an albuminous body 

 (ichthin) is deposited. The membrane is carefully spread on a slide 

 and examined in • 5 per cent, salt solution or in water. 



Preparing Cells of the Vitreous in Cyprinoids.t — Dr. H. 

 Virchow gives the following directions for demonstrating the branched 

 cells found on the surface of the vitreous in Cyprinoids : — (1) Harden- 

 ing. Chromic acid, 2 per cent., Midler's fluid or 1 per cent, sublimate 

 solution. The latter to be warmed to 30° C, and while cooling the 

 preparations freed from sclerotic and choroid, should remain therein 

 for about seven hours. After-treatment with alcohol is not requisite. 

 Gold treatment is inapplicable as it renders the retina inseparable. 



(2) Staining. Slow staining with hematoxylin (followed by im- 

 mersion in 1/2 per cent, alum solution) and eosin (eosin 1, alcohol 

 60, water 160) for twelve hours or more ; transfer to absolute alcohol. 



(3) Mounting. After hardening in sublimate the preparation is 

 spread on a slide and a cover-glass imposed ; it is then transferred to 

 alcohol and removed along with the cover-glass for further treat- 

 ment. 



Preparing Elastic Tissue of the Skin.J — Dr. P. G. Unna 

 demonstrates the elastic tissue of the skin by combining osmium- 

 hardening with staining in an acid solution of dahlia or iodine violet. 

 The solution is as follows: — dahlia, 0*2; aq. dest. and spirit (95 per 

 cent.), aa, 10 -0. Mix and add acid nitric, 2-0; aq. dest., 18*0; 

 spirit 95 per cent., 10*0. The osmium sections are over-stained 



* SB. K. K. Akad. Wiss. Wien, xciii. (1886) p. 28 (2 pis.). 

 t Arch. f. Mikr. Anat., xxiv. (1884) pp. 99-113. 

 % Mouatschr. f. Prakt. Dermatol., v. (1886) No. 6. 



