ZOOLOGY AND BOTANY, MIGKOSCOPY, ETC. 663 



stained with borax-carmine, taematoxylin or ammoniacal picrocarmine, 

 and mounted in glycerin or balsam. In order to kill the animals without 

 contraction, so that they may be suitable for sectioning, the author re- 

 commends benumbing them by pouring spirit into sea water and then 

 hardening, or to pour a hot and strong solution of sublimate over them. 

 Hot sublimate, however, alters the tissues somewhat, especially the epi- 

 dermis, but even by the first mentioned method the epidermis, and also 

 the central nervous system, are not quite satisfactory. For hardening, 

 the author used strong spirit, osmic acid, picro-sulphuric acid, chromic 

 acid, cold sublimate, and then treated the animals with the foregoing 

 fluids or with acetic acid, absolute alcohol, 1 per cent, gold chloride, and 

 a mixture of 1 per cent, osmic acid and of chromic acid 2/1000 For 

 staining, picrocarmine and boras-carmine gave the best results. The 

 former colours badly after chromic acid or sublimate, but after being 

 allowed to act for 24 hours, the hue may be increased by the aid of 

 borax-carmine. Haematoxylin and the anilins were tried on the chromic 

 acid specimens. 



Zacharias' Method of Preparing the Eggs of Ascaris megalo- 

 cephala.* — Dr. 0. Zacharias has discovered an acid mixture which over- 

 comes the resistance of the egg membrane and fixes the egg completely 

 within 25 to 30 minutes. The mixture consist of — alcohol 90 to 100 per 

 cent., 80 ccm. ; glacial acetic acid, 20 ccm. ; osmic acid 1 per cent, 20 to 

 30 drops. A little glycerin or chloroform increases the clarifying power 

 of the mixture. Van Beneden employed a stronger mixture, consisting 

 of absolute alcohol and acetic acid in equal parts, without the addition 

 of osmic acid. 



(1) Ascaris females obtained from the living horse by means of arsenic 

 pills, are placed between two sheets of cotton which have been slightly 

 moistened in a 3 per cent, salt solution, then covered with a bell-glass and 

 exposed one to three hours to an incubation temperature of 25° C. This 

 procedure brings the polar globules to development in the younger eggs, 

 and forces the cleavage in the older eggs. 



(2) After an hour's incubation it is well to preserve a part of the 

 material at disposal. The genital sacs are laid bare by a longitudinal 

 slit in the body-wall opposite the sexual aperture ; the vagina is then 

 cut free from the body, the alimentary tract lying between the two sacs 

 is carefully removed, and the ovarian portions of the sacs are cut off, 

 leaving the uterine portions with their contents for preservation. The 

 anterior ends of the uteri contain eggs in all stages of maturation and 

 fecundation ; the posterior ends contain eggs already beginning to cleave. 

 The killing and hardening process should vary considerably for these 

 different stages. 



(3) It is advisable, therefore, to cut each uterus into thirds, and to 

 expose the anterior third to the action of the acid mixture only 5 to 7 

 minutes, and the posterior third at least 25 minutes. After fixation the 

 anterior and middle thirds are transferred to 30 per cent, alcohol, and 

 after a few hours to 50 per cent, alcohol, in which they may be kept for 

 a long time. Eggs in process of cleavage — foimd in the posterior third 

 — should be removed to absolute alcohol the moment they begin to show a 

 light brown staining. After two or three hours they are to be trans- 

 ferred to 70 per cent, alcohol for preservation. If the acid mixtui-e be 



* Anat. Anzeig., iii. (1888) p. 24. Cf. Amer. Naturalist, xsii. (1888) pp. 277-9. 



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