Dy H. B. FANTHAM. 
and much cogitation on the question, I will now endeavour 
to set forth, not without some diffidence, an interpretation of 
the mechanism of the movements of Spirocheta balbianii 
and 8. anodonte, together with, and supported by, certain | 
(unpublished) observations, also made at Roscoff, on the 
movements of living Gregarines (Selenidiide) of the gut 
of Phascolosomes (P. vulgare and P. elongatum). 
My observations on the movements of the trophozoites of 
the Selenidiide of Phascolosoma, in brief, entirely 
support the views of Crawley as to the movements of 
Gregarines. I saw a slight quantity of gelatinous material 
extruded from the Gregarines as described by Schewiakoff, 
but I cannot believe that such is sufficient to account for the 
elidmg movement of the vermiform trophozoites. In the 
Selenidiide the longitudinally arranged myocyte fibrille 
or myonemes are well marked, and, by their contractions, set 
up pressures in a plane at right angles to the long axis of the 
body. One had ocular demonstration of the result of these 
pressures, for, under favourable conditions, I have seen even 
the somewhat spherical nucleus of the Gregarines altered in 
shape and rendered more transversely ovoid, and vice 
versa. 
Now, it seems to me that these observations have a direct 
bearing on the movements of Spirochetes, though the velo- 
cities of forward movement of Spirochetes and Gregarines 
are very different, the latter being much slower than the 
former. I have already mentioned the occurrence of myo- 
nemes in the spirally wound membrane of Spirochetes. 
These myoneme fibrils, by their shifting or movement of 
pressing inwards or outwards towards the attenuated cylin- 
drical body, set up transverse movements in the periplast 
surface—probably as alterations in the position of the stria- 
tions of the periplast membrane and body generally—in a 
plane at right angles to that of the long axis of the body, 
which axis 1s also that of the forward direction of movement. 
An impulse of this kind, starting at the anteriorly directed 
end, sets up a wave passing backwards towards the hinder 
