SOME METHODS FOB LOWER ANIMALS. 465 



more than an hour in concentrated solution of boracic or 

 salicylic acid. Very dilute osmic acid (e.g. O'l per cent.) 

 gives also good results. The " lateral cells " of the gills are 

 best treated with strong boracic acid solution (five parts cold 

 saturated aqueous solution to one part water). 



BELA HALLER'S Mixture, see 539. 



BROCK'S Medium, 535. 



MOBIUS'S Media, 536 ; the second of these is much 

 recommended by DROST (Morphol. Jahrb., xii, 2, 1866, p. 163) 

 for Cardium and Mya. 



See also PATTEN (Mitth. Zool. Stat. Neapel, vi, 4, 1886, 

 p. 736). Sulphuric acid, 40 drops to 50 grammes of water, 

 is here recommended as a valuable macerating and preserva- 

 tive agent. Entire molluscs, without the shell, may be kept 

 in it for months. 



BERNARD (Ann. Sci. Nat., ix, 1890, p. 191) macerates the 

 mantle of Prosobranchs in a mixture of one part each of 

 glycerin and acetic acid, two parts each of 90 per cent, 

 alcohol and O'l per cent, chromic acid, and forty parts water, 

 which acts in from a quarter of an hour to three hours. He 

 also (pp. 102, 306) uses a weak solution of chloride of 

 ruthenium, especially for nerve tracts, mucus cells and cilia. 

 Alcohol material may be macerated in a mixture of one part 

 glycerin, two of acetic acid, and forty of water. 



Arthropoda. 



835. General Methods for Arthropoda. As general methods 

 for the study of chitinous structures, the methods worked 

 out by Paul Mayer (see 7 and 9, and also 90, 229, and 

 230) are excellent. It is at all events absolutely necessary 

 that all processes of fixation, washing, and staining should be 

 done with fluids possessing great penetrating power. Hence 

 picric acid combinations should in general be used for fixing, 

 and alcoholic fluids for washing and staining. Concentrated 

 picro-sulphuric acid (or picro-nitric) is the most generally 

 useful fixative, and 70 per cent, alcohol is the most useful 

 strength for washing out. 



Alcoholic picro-sulphuric acid may be indicated for fixing 



in some cases. 



30 



