1D) H. B. FANTHAM. 
sometimes performed before fixation with osmic vapour, 
while on other occasions the spreading was deferred till after 
fixation. The latter plan was probably the better. The drop 
of liquid containing the parasites was held, attached to the 
under surface of a carefully cleaned slide, over the mouth of | 
a bottle containing osmic acid in aqueous solution of 2 to 4 
per cent. strength, and fixed for one to four minutes. The 
adherence of the film to the slide, in these cases, was secured 
by the albuminous material naturally occurring in the con- 
tents of the alimentary tract of the Lamellibranchs. At 
other times albuminised slides were used, and the drop of 
liquid containing the parasites was put thereon before fixation 
was attempted. In this way smears containing the parasites 
were placed, with the smear side downwards, in Flemming’s 
solution, in Hermann’s solution, or in a mixture consisting of 
two parts of saturated aqueous corrosive sublimate to one 
part of 90 per cent. alcohol. 
Of the various fixatives used I preferred osmic vapour, next 
mixtures containing osmic acid, and lastly the sublimate- 
alcohol. 
Dried smears, the fixation of which was afterwards com- 
pleted just before staining with pure methyl or pure ethyl 
(absolute) alcohol, also gave, on many occasions, very good 
results. For the structure of the delicate membrane of the 
parasites, however, osmic acid was undoubtedly the best 
fixative, but absolute alcohol also revealed the same. 
Another method of smear preparation was also tried, which 
is really a variation in the manner of securing adherence to 
the shde. A drop of the gut contents or a portion of the 
dissolved style was first fixed with osmic vapour before 
being spread, and then mixed with a drop of glycerine and 
albumen. This glycerine and albumen mixture is_ that 
usually employed for securing the adherence of sections to 
slides. After this the drop was immediately spread, and so 
a thin and even film was obtained. 
To sum up regarding fixation, I obtained excellent results 
from the action of osmic vapour on rapidly prepared fresh 
