THE STRUCTURE OF TRYPANOSOMA LEWISI. 785 
the karyosome not very distinct ; the kinetonucleus is sharp 
and deeply stained, its size the same as after iron-hema- 
toxylin. The body shows blotchy blue granules, varying in 
amount in different specimens. 
Carmine stains.—I have tried picrocarmine and other 
carmine stains on trypanosomes, but have never obtained any 
results worth mentioning. 
One cause of the defective results given by some of the 
stains mentioned above—for instance, Delafield’s haematoxylin, 
safranin, gentian violet—seems to me to be in the fact the 
stain colours the cytoplasmic granules so deeply as to obscure 
other parts, especially the trophonucleus,- which stains less 
deeply. 
It must, I think, be the experience of every one who has 
tried different methods of technique on different objects, as it 
certainly has been my experience, how impossible it is to 
infer or predict the results that a given method will yield for 
a particular object from the results that it yields on other 
objects. This truth is constantly brought home to anyone 
studying trypanosomes, as one so frequently obtains prepara- 
tions in which the trypanosomes are vile, while the leucocytes 
are beautifully stained. Thus in films stained with 'Twort’s 
stain after Hermann’s fluid, the leucocytes leave nothing to 
be desired, while the trypanosomes are useless. Similarly in 
my preparations stained with methylene-blue-eosin the leuco- 
cytes are exquisite. 
I have had some experience of the results of techmique on 
another class of objects which might be expected to be not 
so different from trypanosomes in their reactions, namely, the 
collar-cells of sponges. A collar-cell is a flagellate organism 
which might be described as possessing a non-undulating 
membrane, perhaps similar, morphologically, to that of 
trypanosomes, but not connected with the flagellum and not 
contractile in the same manner, only slowly retractile. Noa 
priori reason presents itself to me that would lead me to 
expect a trypanosome and a collar-cell to be very different in 
their staining reactions. 
