NEW TYPE OF PROTISTAN PARASl'I’E. 
453 
different, with their granular cytoplasm. In this respect 
Selenomastix agrees with many bacteria, though it so 
happens that spirilla, especially the larger ones, are often 
distinctly g’ranular and sometimes exhibit a chambered 
structure, of which there is no sign in this new form. 
The principal differences from the spirillar type are as 
follows : There is no true spiral form of the body, or indica- 
tion of spiral movement. In some individuals, however, there 
is a hint of a twisting of the axis towards one end, which 
may or may not represent a permanent condition. There are 
no terminal flagella, but a single more or less median one. 
There is distinct evidence of antero-posterior orientation. 
On the other hand, we have never observed the reversal of 
direction characteristic of spirilla. Another important dis- 
tinction is that both the crescents and the ovals can move by 
means of the body alone, resembling a Spirochete, with 
which, however, Selenomastix has assuredly nothing else 
in common. Again, individuals certainly vary in width as 
well as in length; broadly speaking, the larger individuals 
are both longer and wider than the smaller ones ; this is 
apparent from our plates. Last, but not least, no spirilla of 
any kind hitherto described, so far as we know, have any 
phase connected with them comparable to the ovals of 
Selenomastix. 
With regard to the vexed question of plasmolysis, we are 
inclined to think that this occurs, at any rate in the ovals. 
In living preparations which have been made for some time 
(whether diluted with a drop of normal saline solution or not), 
a small proportion of the ovals show a vacuole, or space-like 
appearance near one or both ends ; this is most probably due 
to the shrinkage of the protoplasm away from the envelope. 
When the parasites are placed in 5 per cent, or in 10 per 
cent, salt solution, a somewhat larger proportion of the ovals 
show this shrinkage appearance, and it is evident, also, here 
and there in a few crescents. Many of the ovals, however, 
and the great majority of the crescents — chiefly those, we 
think, in which, if stained, the envelope would not stand oft’ 
