144 THE NAUTILUS. 



colors of the nudibranch should be preserved as faithfully as 

 possible. Two fluids which I have found useful with Chromo- 

 doris zebra are Merkel's fluid and the sublimate-acetic mixture 

 (saturated aqueous solution of sublimate plus 5 per cent glacial 

 acetic acid). The sublimate mixture in particular gives a very- 

 fair preservation of the blue pigment of Chromodoris, which is 

 permanent for six months at least, if not for a longer period. 

 The sublimate precipitates the blue substance so that it is no 

 longer soluble in aqueous alcohol, and at the same time renders 

 it insensitive to the acetic acid, which otherwise would cause 

 the substance to become pink. Possibly the platinic chloride 

 in Merkel's fluid has a similar action, since I find that both 

 mercurous salts and platinic chloride precipitate the blue pig- 

 ment from aqueous solutions. 

 Agar^s Island, Bermuda. 



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