H. A. Baylis 407 
them to die in an expanded condition. The worms can be left in the sublimate 
mixture for a few days if desired, or may be transferred to water after a few 
minutes. In either case they must be washed in running water for 12-24 hours, 
or transferred to 70 per cent, alcohol in which enough iodine has been dissolved 
to give it the colour of sherry. This should be changed repeatedly until the 
colour of the iodine ceases to disappear. Finally the specimens should be 
stored in 70 per cent, alcohol. 
The following alternative methods are recommended for trematodes by 
Braun and Liihe. 
(1) Wash in normal saline, brush off mucus, etc., and stretch on a slide. 
Put a drop of the fixing fluid on a coverglass, and apply it with slight, but not 
excessive, pressure, using paper supports or small weights as required, ac¬ 
cording to the size of the worms. [For large, fleshy forms, pressure between 
two slides, by means of rubber bands or thread, may be employed.] Add more 
fluid at one edge of the coverglass, drawing it off with blotting-paper at the 
opposite edge. 
The fixative recommended by these authors is Hofer’s (saturated watery 
solution of picric acid, 50 parts; water, 48 parts; glacial acetic acid, 2 parts). 
When the worms are rigid, wash off the slide into a dish of the fluid, and allow 
this to act until the entire worm is opaque. Then wash in water for a few 
seconds, and bring up through 45-50 per cent, alcohol to 70 per cent, alcohol, 
and change this frequently to remove the yellow colour of the picric acid. 
(2) Another fixative, which is especially useful for demonstrating yolk- 
glands, and may be used in the same way as the last, is Muller’s fluid (potassium 
bichromate, 2-5 parts; distilled water, 100 parts; sodium sulphate, 1 part). 
The worms should be soaked in this until the yolk-cells have become brown, 
then washed in running water and dehydrated with increasing strengths of 
alcohol as before. 
If other fixatives are not at hand, hot or cold alcohol may be used; or 
formalin (10 per cent, solution) may be substituted for the corrosive sublimate 
mixture in the first method, and the worms afterwards stored in 3 per cent, 
formalin. 
Cestodes. 
After washing the worms, the main difficulty is to keep them straight and 
extended, and to avoid tangling. This may be accomplished either by laying the 
specimens out, slightly stretched, on a plate of glass or porcelain, and pouring 
the fixative over them, or, better, by picking up each worm by the end remote 
from the scolex and allowing it to hang down, when its own weight will usually 
cause it to stretch sufficiently. It may then be dipped quickly several times 
into a jar of the fixing fluid. Small forms, whose weight is not sufficient to 
stretch them, may be drawn along the side of the vessel after each dipping, 
so as to exert a slight longitudinal pull on the strobila. Very long specimens 
may be wound spirally round a wide glass tube or bottle before fixation, and 
the whole immersed in the fixative. When the worms cease to show any sign 
