21% 
animals being, as known, provided with a very thick cuticula it is 
of importance to find well penetrating fluids; this is not the case 
with osmic acid. This fluid, in my opinion, can only be employed 
upon diminutive species and in this case, in accordance with the 
well known method employed on Protozoans, namely on the slide with 
osmic vapour by holding the slide inverted over the mouth of a 
bottle containing a 1 per cent solution of osmic acid, for five mi- 
nutes. Ås far as my experience goes, the same fluid that can be 
used for some forms cannot be employed with success on all. One 
of the mixtures which has most satisfied me and which I used for 
a long while is a mixture of a saturated solution of Picric acid 
3 and glacial acetic acid 1. It has the advantage that it kills 
the Nematodes instantly and that the animals always assume their 
natural shape, viz. either stretched out or more or less curved, as 
the stiff cuticula will permit, without incalculable torsions caused 
by contractions of the muscles, which can be of the most disturbing 
effect when the animals are to be mounted on the slides. The 
mixture will also bring about a profitable differentiation so that 
the nrgans, often even the nuclei of the cells will appear distinctly. 
The weak point is that some shrinking is inevitable. I shall here 
add, that 1 never — as is generally recommended — apply the 
mixture from the edge of the cover-slip. I take the animal with 
a needle and put it direct into a watch-glass, filled with the fixa- 
tion-fluid. 
On account of the above mentioned shrinking I have of late 
employed the following mixture: Formaline, 6, Alcohol 90 Yo, 20, 
glacial acetic acid, 1 and aqua destill., 40. This I find gives very 
beautiful results. — Boiling with Alcohol after the method of 
Loos, that has proved so excellent for the greater parasitic forms 
is not applicable to the case under consideration. After fixation I 
remove the animals into a mixture of Glycerine, 1, Alcohol 90 "Yo, 
1, Aqua destill. 2 for evaporation, and thereafter they are mounted 
on the slide in pure Giycerine or Glycerine-Gelatine. 
In spite of all pains taken 1 have not succeeded in getting 
