98 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. Osmic 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, " Mittheilungen 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 Royal 
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 Dredge. — 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 naps 
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, per cent., or 70 per cent, alcohol, 100 ccm. ; tincture of 
iodine, 2 5 ccm. 
