158 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Preparing Silkworms.* — Mr. A. C. Cole gives the following 



methods of preparation : — 



The silkworms are to be hardened in spirit ; the parts intended to 

 be mounted are then to be cut, or dissected out, and placed in liquor 

 potassae for from thirty-six to forty-eight hours; then thoroughly 

 washed and cleaned with a soft brush, then soaked in distilled water, 

 to be once or twice changed, during three or four hours ; then placed 

 in acetic acid ; next in water, to remove the acid ; next in spirit, for 

 re-hydration ; next in oil of cloves ; next in turpentine, and mounted 

 in balsam. 



When the tracheal tubes only (separated from the spiracle) are 

 required for study, it is better to mount them in a cell, in glycerin 

 jelly, and they should be placed, after the acetic-acid treatment, in a 

 mixture of haK glycerin and half water, with a slight addition of 

 acetic acid, until all trace of air is removed. 



Preparing Alimentary Canal of Crustacea.t — For hardening 

 the river cray-fish, Dr. J. Frenzel recommends Kleinenberg's picro- 

 Bulphuric acid diluted with only twice 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 chromic solu- 

 tions 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 prepared for surface-examination. 



For imbedding, paraffin is to be preferred to celloidin. Precaution 

 should always be taken to prevent the formation of large crystals, 

 which not only render the paraffin brittle, but also injure the finer 

 structure of the preparation, by immersing it in cold water and cutting 

 soon afterwards. If the paraffin block is allowed to stand for weeks, 

 crystallization sets in. 



In staining, the sections are fixed on the slide with chrome 

 mucilage, and then stained with alum carmine, alcohol carmine 

 (Grenacher), aqueous haematoxylin (Bohmer), and safranin. For the 

 epithelium of the middle gut, a double stain with acid carmine and 

 hsematoxylin offers some advantages. 



Preservation of Medusae. J — Dr. W. Haacke preserves Medusas 

 in the following way, by which they are said to retain their shape 

 better than by any other method known. 



The MeduEse are placed in a vessel of sea-water, and killed by the 

 addition of a few drops of concentrated solution of chromic acid; 

 they are then placed in fresh sea-water, which is repeatedly changed 



* Cole's Studies in Microscopical Science, iii. (1885) sec. 4, p. 34. " The 

 tracheal system in our present preparation would have been thus mounted, but 

 balsam being calculated to display the structure of the spiracle and foot to 

 greater advantage, it was considered advisable to employ that medium." 



+ Amer. Natural., xix. (1885) p. 1246. From Arch. f. Mikr. Anat, xxv. 

 (1885) pp. 141-3. X Zool. Anzeig., viii. (1885) pp. 515-6. 



