436 
H. WOODCOCK AND G. L ADAGE. 
least common type of movement, but we regard it as very 
important, since it provides a distinct indication of antero- 
posterior polarity. (2) The body oscillates to and fro, or turns 
round completely, one and a half times, or even twice, in the 
plane of its long axis, i. e. turning a somersault as it were ; 
no forward progression is effected. This movement may be 
quite rapid. When it can be seen, the flagellum stands out 
well from the body; it may cause this movement, but we feel 
undecided, for we have noticed that when a crescent is 
becoming a little sluggish and the oscillations take place at 
longer intervals and not so rapidly, a premonitory tremble 
of the body occurs the instant before the movement. (3) Some 
parasites, which are moving only at intervals, can be seen to 
turn slowly from one side to another, this time around the 
long axis. In these cases the flagellum appears to be quite 
passive, and to turn over after the body. We certainly 
consider this movement is caused by the body and not by the 
flagellum. Moreover, now and again a crescent can be seen 
oscillating more or less, when it is impossible to see a flagellum 
in connection with it, and though ot‘ course it is sometimes 
difficult to make out the flagellum, nevertheless, with the aid 
of good lenses and critical illumination, this can usually be 
clearly seen ; further, crescents without a flagellum do 
undoubtedly occur. Hence we feel persuaded that move- 
ments caused by the body alone and not by the flagellum do 
take place (cf. also the ovals). 
The movements of most of the crescents cease very soon 
after being removed from the rumen — surprisingly soon in 
some cases. After about an hour few are still to be found 
active, and their movetnents have become irregular and 
spasmodic. Even in a quantity of the fluid contents kept in 
a warm water-bath, at from 30°-35°C., in three or four houi-s 
the parasites were all motionless. Crescents may have short 
resting intervals and may then become actively motile again • 
but when all or nearly all the crescents in a particular area 
of the drop under examination remain motionless, they may 
be regarded, we think, as being dead. In the rumen-contents 
