MICROSCOPICAL TECHNIQUE. 339 



After the Ctenophores have been properly preserved, precau- 

 tion must be taken in transporting them, for they are easily torn to 

 pieces. If they are placed in bottles filled with fluid of the proper 

 density and the cork so inserted as to leave no air-bubbles, this 

 danger is reduced to a minimum." 



Preservation of Sea-Weeds.^— Dr. J. P. Lotsy recommends the 

 following method of preserving specimens of Floridece, which 

 prevents swelling of the cell-walls or contraction of the protoplasm, 

 and preserves the chromatophores uninjured. The specimen is 

 first laid in a i per cent, solution of chrome-alum in sea-water, 

 and kept there for a period varying from one to twenty-four hours, 

 according to the size and texture of the species. The chrome-alum 

 is then completely washed out, and the specimen placed in a 

 mixture of 5 ccm. of 96 per cent, alcohol in 100 ccm. water, and 

 vigorously stirred. The amount of alcohol is then increased by 

 increments of 5 ccm. every quarter of an hour until it amounts to 

 50 ccm. The specimen is then removed, and placed in a mixture 

 of 25 per cent, alcohol in distilled water, and the quantity of 

 alcohol again increased in the same way till it amounts to 50 ccm. 

 alcohol to 100 ccm. of water. The same process is again repeated 

 with 50, 60, 70, 80, and 90 per cent, solutions of alcohol in dis- 

 tilled water, the specimens being finally preserved in the last. 



Staining and Fixing Diatoms. t— Dr. P. Miquel finds the 

 staining reagent best adapted for demonstrating the gelatinous 

 envelope of diatoms to be an aqueous or boric solution of methylin- 

 blue, which is not taken up so readily by the gelatinous stipe. 

 The same reagent, especially in a slightly ammoniacal solution, 

 may be used for demonstrating the nucleus, which is stained blue, 

 while other substances contained in the cell take from it a dark 

 blue violet stain. For fixing, the author uses a solution of 65 gr. 

 corrosive sublimate and 15 gr. sodium chloride in 100 ccm. of 

 water. 



^ Bot. CentralbL, LX. , vide Journ. R.M.S., 1895. P- ^S^- 

 tZ^ Diatoniiste, 11., 1894, vide Journ. R.M.S., 1895, P- ^27. 



