CUTTING SECTIONS OF THE EYE. 313 



allowed to dry. In the mean time prepare a solution of alum as fol- 

 lows : Take 25 grams of alum, and after it has been thoroughly 

 pounded in a mortar pour it into 250 cc. of distilled water. To 

 this solution add strong potash until a precipitate is formed, which 

 will not dissolve upon stirring and-standiug. 



" Pour the alum solution thus made on to the hsematoxylin 

 residue, and allow it to macerate for three or four days in a 

 warm room. Then niter the hsematoxyliu solution into a bottle 

 provided with a closely-fitting stopper, and add to it 10 cc. of pure 

 glycerine and 100 cc. of 90 per cent spirit. (The residue need not 

 be thrown away, for it can be macerated again with alum solution 

 for a week or more, and a good strong stain obtained as before.) 

 When the solution is thus made it should be well shaken and allowed 

 to stand for some weeks before being used. This solution of hsema- 

 toxyliu improves considerably with age. The oldest I have was 

 made about twelve mouths ago, and is by far the best. 



" The haematoxylin stain produced by this recipe possesses several 

 advantages over others. In most cases it differentiates the tissues 

 admirably; nuclei stain deeply, cell protoplasm faintly; it seems to 

 last a long time without showing signs of fading, and, as it pene- 

 trates well, it is very useful for staining in bulk." 



Dr. J. S. Kingsley's* method of preparing and cutting the eggs and 

 embryo eyes of the shrimp, which will also apply to the embryonic 

 eyes of insects, is as follows: 



The eyes were hardened by means of Perenyi's fluid, followed by 

 alcohol of increasing strength, a process which works well with 

 almost all Arthropod tissues. In most instances, they were stained 

 entire with Grenadier's alum-carmine, though in some instances 

 Kleinenberg's hoernatoxylin or Grenacher's borax-carmine were em- 

 ployed In the later stages, where the deposition of pigment in the 

 eye interfered with a clear vision of all the structures concerned, the 

 following course was adopted : The eyes were sectioned as usual, 

 the sections being fastened to the slide with Mayer's albumen fix- 

 ative. After wetting the paraffine and allowing the sections to drop 

 into the adhesive mixture,, the embedding material was dissolved in 

 turpentine, and this in turn was washed away with alcohol (95 per 

 cent). The sections were then covered with a mixture of equal parts 

 of nitric acid and 95 per cent alcohol, which was allowed to remain 

 until the pigment was removed, a process requiring from ten to 

 fifteen minutes. The slide was next washed with strong alcohol, 

 and the sections stained deeply with Kleinenberg's hrematoxylin, and 



* Journal of Morphology, Boston, 1887, 49. 



