508 SUMMARY OF CURRENT RESEARCHES RELATING TO 



pipette, absorbent paper, and partial evaporation, oil of cloves is added, 

 and tbo specimen mounted in balsam. Tbe lingual membranes will 

 be found more or less coiled, and usually attached to the jaws. It is 

 desirable to have the membrane flattened out, with the dentiferous side 

 uppermost, and dissociated from the jaws. Some species have a large 

 strong jaw, which, if left with the lingual membrane, will raise the cover 

 so far above the denticles as to prevent the uso of high powers. It is 

 therefore necessary to unfold the radula and remove the jaw. Having 

 provided a clean glass slide on the turntable, the specimen is taken from 

 the clove oil and centered on the slide. The radula is then easily 

 unrolled with needles under a Microscope provided with an erector, and 

 the jaw removed. Replaced on the turntable, a thin cover-glass is 

 imposed and centered. This should be done before the balsam is added, 

 as it prevents the specimen from again becoming coiled or displaced. A 

 drop of balsam in benzol is put adjacent to the edge of the cover, and 

 the slide held an instant over a gas-burner or spirit-lamp, which will 

 cause the balsam to flow under the cover. A spring clip is then put on 

 to fix the cover down. The slide is next removed to an oven and left 

 until the balsam has hardened, so that the portion outside the cover can 

 be scraped off. The slide is then cleaned by washing in strong spirit, 

 and dried with soft tissue paper. The cover-glasses should be of known 

 thickness. Many radulae require a 1/10 in. objective. The con- 

 vexity of the object, combined with the thickness of the cover, 

 necessitates the use of very thin glass. For the Eissoiidte the author 

 usually employs glass of • 004 in. thickness. 



Some good preparations were obtained by using nitrate of silver 

 instead of chromic acid as a staining reagent, but the specimens require 

 boiling in the silver solution, and this additional step further compli- 

 cates the process and makes it less possible to retain small specimens. 

 Besides, too much action of the silver renders the objects opaque. 



Preparation of Cypridinse.* — Dr. A. Garbini examined fresh teased- 

 out tissue in sea water. Maceration was effected in a small quantity of 

 one-third spirit. The best fixative was found to be a watery solution of 

 sublimate. In this the animals were left for 5 to 7 minutes, and then 

 transferred to distilled water, and afterwards, to 75 per cent, alcohol, 

 with a trace of tincture of iodine, and finally to pure 75 per cent, 

 alcohol. Good results were obtained from Mayer's fluid (Kleinenberg's 

 mixture with sulphuric acid), but the epithelium of the digestive tract 

 was less well fixed. The preparations were imbedded in paraffin by 

 Giesbrecht's method. 



Preparing Ova of Ascaris megalocephala.f — Prof. E. van Beneden, 

 in his further researches on the ova of Ascaris megalocejjhala, treated the 

 fresh ova with glacial acetic acid or with an equal mixture of crystal- 

 lizable acetic acid and absolute alcohol. After twenty minutes, when 

 fixing had taken place, the acid was replaced by a third part of glycerin 

 in water, and by aqueous solution of malachite-green, or of vesuvin, or of 

 both together. The staining soon takes place, and if it be allowed to go 

 too far can be readily washed out. If glycerin be rapidly substituted 

 after five or ten minutes, the ova although stained will go on segmenting, 

 and even form normal embryos. 



* Bull. Foe. Entomol. Ital., xix. (1887) pp. 35-51 (5 pis.). 



t Bull. Acad. R. Sci. Belg., xiv. (1887) pp. 215-94 (2 pis.). Supra, p. 423. 



