as Infusoria flagellata. 139 
The flagellum (ff) has more of a sigmoid flexure than that 
of Monas termo (figs. 1-4), and about as much as that of An- 
thophysa Miillert, Bory (figs. 47, 48, ff). It arises from the 
axial point of the front, and extends to about three times the 
length of the body. The plane of its curve bears the same 
relation to the mouth and lip as that of Monas termo, and it is 
used in the same manner as a prehensile organ to assist the 
iP (fig. 6, /p) when taking food, and for a propelling-apparatus 
( 4 5°, ft), as the body whirls along after 1t during natation. 
he mouth (fig. 6,m) lies in the same relative position as 
that of Monas termo, and receives its food in pibeiaity the same 
manner, and, by the assistance of the lip (Jp), with the same 
degree of rapidity passes it into the body. . 
he contractile vesicle (cv) lies on the same side of the plane 
of the arcuate flagellum (//) as that of Monas termo, and at 
about the same distance from the front, but in an opposite 
region, and directly in the antero-posterior line with the lip. 
It is also a more vigorous and larger organ than that of the 
other Monas ; and, bulging out (fig. 5*, cv) the body even more 
strongly during expansion, its systole takes place at double 
the rate (that is, twelve times, a minute), and very abruptly. 
The pedicel (pd) sometimes attains to four or five times the 
length of the body, but most frequently it is not more than half 
as long as that. It is thin and delicate, but appears to possess 
considerable rigidity, either in a fully ee state, or when 
(as appears to be the case sometimes) it is contracted into more 
or less abrupt curves (fig.6, pd). ts apex (fig. 5, pd") is 
attached to the posterior end of the body, at a point which is 
coincident with the longitudinal axis. 
: 
* 
es 
t 
§ 3. Bicosaca, nov. gen.* 3 
Bicoseeca gracilipes, nov. sp. Pl. V. figs. 34, 35. 
_ This genus might be compared to a Monas seated in a calyx, 
and upon a highly muscular, contractile stem. 
Bicoseca gracilipes is a marine form, and has thus far been 
found, although in considerable numbers, only upon Sertularia 
_ eupressina, Linn. It is an excessively minute creature, as may 
be readily judged by the reader upon referring to the magnify- 
_ ing powers which are laid down in the description of the 
_ figures. When first met with, it appeared, upon a casual ob- 
_ servation and under a magnifying-power of only five hundred 
_ diameters, to be an elongate, naked Monas, which was kept in 
a firm pe by some invisible fore It soon, however, 
_ attracted particular attention to itself by its peculiar, spasmodic 
* Bixos, a vase ; oixéw, to inhabit. 
