No. 1.] TWO NEW GREGARINIDA. 13 
The strength of the gregarine was well shown in one case 
where, after having fastened its head to the slide, it raised the 
middle portion of its body and turned it through an arc of 180°, 
like the bail of a bucket, its head and the tip of its tail alone 
resting on the slide during the process (PI. III, Fig. 52). From 
the fact that the general shape of the animal did not change 
during the operation, it is probable that the entire movement 
was caused by the contraction of a very small portion of the 
body wall. The area of contraction must have been limited to 
the region of a (PI. III, Fig. 52), since the head alone was fixed, 
the tail being free and changing its position slightly. 
The most interesting movement observed, however, is that 
of locomotion. It is a “very slow movement of translation in 
a straight line’ without any apparent contraction of the walls 
of the body. It is probably caused by a very slight undulatory 
motion of the under surface of the animal. 
My material, obtained at Woods Holl, was all collected in the 
months of July and August. Perhaps this is the reason why I 
have not found the encysted stage of this gregarine. 
This work was begun in the summer of 1891 at the sugges- 
tion and under the direction of Dr. C. O. Whitman; it was 
completed during the past winter under the very kind and care- 
ful supervision of Dr. E. L. Mark in the zodlogical laboratory 
of Harvard College. I wish to express a deep feeling of 
indebtedness to my instructors for whatever there may be of 
value in this paper. 
CAMBRIDGE, Mass., 
May 21, 1895. 
