NOTE ON THE STAINING OF FLAGELLA 157 
When this 'swollen membrane' is visible the flagella appear to be prolongations 
of it and to have no connection with the protoplasm of the body or the organism. 
4 I isolated from sewage a spirillum, which, in liquid media, developed a 
very long terminal flagellum, and this flagellum was plainly visible in every specimen 
stained in the ordinary way, i.e. without the use of' mordants.' This flagellum must 
then have been composed of a substance quite different from that of the flagella of 
other organisms, a substance which absorbed ordinary dyes ; or it must have had the 
same composition as any other flagellum and have been visible merely because it 
was thicker. No adequate proof has been brought forward that the flagella of various 
organisms differ in their composition, and therefore the reasonable presumption is 
that it was its breadth which rendered this flagellum visible. 
Unfortunately, circumstances prevented for a time further experiments with 
this organism, and it died. I have not had an opportunity of trying the effect of 
' mordants ' on it. 
For these reasons I venture to suggest that the present ideas of flagella 
staining may be wrong, that flagella may stain with the ordinary dyes, but are invisible 
on account of their fineness, and that the so-called ' mordants ' may act merely by 
causing the flagella to swell and thus become visible when stained. 
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