106 METHODS OF COLLECTING AND PRESERVING 



iodized alcohol (the recipe for which is given below *), to remove all 

 traces of sublimate, which in alcohol crystallizes out in the tissues 

 of the organisms, and so injures the preparation. 



Chromic acid, 1 per cent, solution : objects must not be left in too 

 long, or they become brittle ; after immersion they must be washed 

 in distilled water before being put into alcohol. 



Glacial acetic acid suddenly kills animals plunged in it (see 

 " Tunicata "). 



Osmic acid, 1 per cent, solution, kills and fixes small gelatinous 

 organisms. Too prolonged use renders them brittle, and causes them 

 to assume a dark brown tint. Objects should be washed in dis- 

 tilled water before placing them in alcohol. t)smic acid vapour is 

 irritating to the eyes and organs of respiration. 



For further information on mixtures for killing, fixing, and 

 hardening used at the Zoological Station of Naples, see : — 



Lo Bianco, " Mittheikmgen Zoologische Station, Neapel," 1890, 

 Band IX., pp. 435-474; full abstract of this paper in "American 

 Naturalist," 1890, XXIY., pp. 856-865, and in "Journal of Koyal 

 Microscopical Society," 1891, p. 133. A verbatim translation into 

 French is in " Bulletin Scientifique de la France et de la Belgique," 

 1891, Vol. XXIII., pp. 100-147. 



APPARATUS FOR COLLECTING. 



The Dred(je. — This apparatus consists of a net fastened to a 

 rectangular iron frame, by which its mouth is kept open ; hinged to 

 the frame on each shorter side is an arm, to one of which the 

 hauling-rope is attached. The net is protected by two flaps 

 of canvas, which are attached to the frame and extended a little 

 beyond the net all round, the flaps being tied together here and 

 there at the lateral edges. The best and most practical account 

 of a good dredge and how to make it is that of Mr. W. H. Dall in 



* Iodized alcohol has the following- cooipoi^ition : — 35 per cent, or 70 per 

 cent, alcohol, 100 com. ; tincture of iodine, 2*5 com. 



