H. A. Baylis 405 
causing undue shrinkage. Since this cannot be done equally well for all the 
groups by any one method, the various groups must be dealt with separately. 
-N-I3. Corrosive sublimate (percliloride of mercury) forms the basis of 
many of the methods in general use. It should be remembered that when 
this substance is used the specimens should not be handled, at any time during 
the process, with metal instruments. They may be moved about by means of 
a splinter of wood, a quill, or a glass implement. 
Nematodes. 
Owing to the peculiarly resistant cuticle, rapid penetration is not easily 
effected by cold solutions, and hot fixatives are essential if good results are to 
be obtained. Elaborate cytological fixatives possess no advantage for ordinary 
purposes. No method has yet been devised which gives better results than 
the simple one introduced by Looss—viz., immersion in hot 70 per cent, 
alcohol. The spirit should be heated until it is steaming, but not boiling. 
A temperature of 50°-60° C. has been recommended, but Dr Boulenger con¬ 
siders this is not quite sufficient, and prefers 70° C. 1 When of fair size the worms 
should be picked up separately with forceps (without using pressure), or with 
a needle, and dropped into the previously heated spirit. The dish 2 in which 
the spirit is contained should be of sufficient width at the bottom to enable 
the worms to straighten out, which they usually do almost at once. The fluid 
is allowed to cool, and the specimens then bottled in fresh 70 per cent, alcohol. 
When the specimens are small and numerous, it is not necessary to remove 
them entirely from the food-remains and other debris with which they are 
frequently mixed. In such cases it is easier, after draining off as much as 
possible of the washing fluid, to pour the hot alcohol over the material. When 
cool, the whole may be poured into a tube or bottle, and allowed to settle. 
The used fluid may then be replaced by fresh. 
In the case of small specimens, it is sometimes an advantage to use a 
5 per cent, solution of pure glycerine in 70 per cent, alcohol, instead of the 
plain alcohol. The method of procedure is the same. 
These methods almost entirely avoid shrinkage or collapse of the specimens, 
if they be alive immediately before fixation, and usually cause them to die 
in a straight and extended condition. 
For storage the worms may usually be kept in good condition in pure 
70 per cent, alcohol, but in hot climates or when some time is likely to elapse 
before the tubes or bottles are unpacked, it is preferable to add glycerine in 
the proportion of 5 per cent, to the 70 per cent, spirit. This prevents the 
drying-up of the material, and keeps it in good condition for examination, 
while, when small specimens are to be examined in glycerine, the alcohol and 
water may simply be allowed to evaporate slowly, leaving nearly pure glycerine. 
1 The temperature originally recommended by Looss was 80°_90° C. 
2 For travelling purposes, enamelled iron dishes, which can be heated over a spirit lamp will 
be found useful. 
