1246 General Notes. [ December, 
MICROSCOPY :! 
THE ALIMENTARY CANAL OF THE CRUSTACEA —1. Hardening.— 
For the river cray fish, Frenzel? recommends Kleinenberg’s picro- 
sulphuric acid diluted with only two times its volume of water. The 
preparation is left fifteen minutes in the fluid, then treated with 
the usual grades of alcohol. Osmic acid and the various chro- 
mic solutions proved worthless. Perenyi’s fluid caused a slight 
swelling, but was of some service in the study of the liver and 
the nuclei of the middle gut. Corrosive sublimate (saturated 
aqueous’ solution) proved an excellent means of isolating the 
epithelium of the middle gut in the lobster. In preparations 
hardened in this fluid the epithelium becomes loosened from the 
wall of the canal, so that it can be stripped off in sheets and pre- 
pared for surface examination, 
2. Imbedding —Paraffine is preferred to celloidin. Precaution 
should always be taken to prevent the formation of large crys- 
. tals, which not only render the paraffine brittle, but also injure 
the finer structure of the preparation, by immersing it in cold 
water and cutting soon afterward. If the paraffine block is 
allowed to stand for weeks crystallization sets in. 
3. Staining—The sections are fixed on the cs with chrome 
mucilage, then stained with alum carmine, alcohol carmine 
(Grenacher), aqueous hematoxylin (Bohmer) ad sahin. For 
the epithelium of the middle gut a double stain with acid car- 
mine and hæmatoxylin offers some advantages. 
FRENZEL’S CHROME MuciILacE As A Fixative.2—Make a thin 
solution of gum arabic in water and add to this an aqueous solu- 
tion of chrome alum. An excess of the latter does no harm. 
little glycerine is added to the mixture to prevent it from drying 
too rapidly when painted on the slide. 
‘After painting the slide with a small brush the sections are 
placed in order and the slide left for a few minutes (not over fif- 
teen minutes) in the oven of a water-bath kept at 30-45° C. The 
gum is thus rendered insoluble. The paraffine is next removed 
in the ordinary way and the sections stained according to 
desire. Fuchsin and safranin are the only analine dyes which 
cannot be used, as they stain the film of gum deeply and thus 
injure the preparation. 
. Tae RETRACTILE TENTACLES OF THE PuLMONATA.—The retrac- 
organs, as is well known, are hollow cylinders, 
. C. O. WHITMAN, Mus. Comparative Zoology, Cambridge, Mass. 
inat., XXV, p. 141-143, e 1885. 
nal e ty eg 188 
h 4405 5 Zeitschr, f. wiss. Zool., 1872, XXII, p. 366. 
