as Infusoria flagellata. 141 
itself. Within this broad space the simple mouth (m) is 
situated. 
The flagellum (fl) is the most active of the prehensile organs, 
and the only vibratory filamentous body which this animalcule 
possesses. In length it is about three times that of the body, 
or a little more, and projects far beyond the rim of the vase (c). 
It is a curious fact that while in Monas and Anthophysa the 
lip and flagellum lie closely together, they stand far apart in 
Licoseca. The flagellum is not an undulatory, vibrating 
organ, in the common sense of the term, but usually supports 
itself in a rigid condition, except at the tip, which is kept in 
nearly constant motion, incurvating with frequent jerks, and 
tossing floating particles toward the mouth. Its ‘ial two- 
thirds is quite strongly curved, but not so much as to be abso- 
lutely falcate; and at its basal third it is moderately arcuated 
in the opposite direction, so that the whole flagellum has a 
_ slightly sigmoid flexure. The plane of this curve is such as 
_ to strike the mouth and lip when carried out in that direction. 
_ The diameter of this organ is about equal from tip to base, 
_ excepting a slight thickening at the latter point. The only 
times that the flagellum abandons its rigid deportment are either 
when it is assisting the lip to seize the food, or during the 
. retrocession of the body. In the latter case it is 
abruptly retracted and coiled (fig. 35, #) transversely within 
the calyx (c) close down to the truncate front of the body: 
When the latter slowly pushes forward from the bottom of its 
_ dormitory, the flagellum as deliberately uncoils, and at first 
_ vibrates with a rapid wriggle, but finally assumes its former 
_ sigmoid curve and rigid deportment. 
The mouth (m), as has already been mentioned incidentally, 
lies in the middle of the truncate front, and consequently faces 
_ toward the aperture of the calyx (c). Food is brought to it by 
means of the flagellum (ff); and the latter and the lip (dp) 
force it into the oral aperture exactly in the same way as has 
been described in regard to Monas. 
__ The contractile vesicle (cv) is a single globular organ, which 
lies on the corresponding side of the body with that of Monas, 
and just in front of the middle. In full diastole its diameter 
equals one-third of that of the body. Both the systole and 
diastole are very slow. 
The calyx (c) is about twice as long as the body which it 
encloses, and between four and five times its own average 
diameter. It has the form of a very deep slender urn, with a 
rounded bottom, slightly contracted waist, and a very delicate, 
_Searcely reverted, truncate rim. It is so hyaline and faint that 
it almost defies any magnifying-power below that of eight 
Ann. & Mag. N. Hist. Ser. 4. Vol. i. 11 
