332 
MR. j. i)alrymple;’s description of an infusory 
flask, pellucid in the highest degree, possessing no colour except what is due to a 
small pink eye and to the stomach, which varies in hue according to the food, but 
generally of a yellowish brown hue. When seen laterally, or in profile (if one may 
so say), the lower part is not equally convex, for it slopes off from one side, so that 
the most inferior part of the outer case is somewhat oblique, and one side somewhat 
longer than the other. It is towards the inferior part of this longer side that an open- 
ing (Plate XXXIII. fig. 1 S), valvularly closed, is observed in profile, which, when seen 
in front, is represented by a semilunar slit (Plate XXXIII. fig. 2 H), whose concavity is 
turned downwards ; this is the vaginal aperture, whence the embryo, when mature, 
or the ova, are expelled. Each leaf of this valve is provided with special muscles 
for opening it, while it appears to be kept closed partly by its own elasticity, and 
partly by the pressure of the fluid contained in the body of the animalcule. Upon 
tlie hyaline tegument of the body may be seen, faintly indicated, transverse or cir- 
cular bands or rings (Plate XXXIII. fig. 1 R) that mark the points where folds are 
developed upon muscular contractions of the animal, and it is on the inner side of 
this tegumentary covering, at the place where the rings are seen, that the long, 
ribbon-shaped muscles are symmetrically attached (PlatC'XXXIII. fig. 1 M). 
The principal movements of progression are effected by means of the ciliary or 
rotatory apparatus, at the head or superior extremity of the body, and which seem 
to be independent of the more special rotatory mechanism, whereby two currents are 
produced in the water, that draw within their influence the smaller animals that 
serve as food : on reaching the point where the two opposite moving vortices meet, 
the food is immediately directed backwards in a straight line intermediate between 
the two, and so enters the oral orifice of the animal (Plate XXXIII. fig. 1 B). There 
seems however to be a distinct power of selection, for the slightest lateral movement 
of the head of the animal enables it to avoid objects too large for admission, or which 
it wishes to reject. 
The cilia, by which all these motions are effected, appear to be placed upon raised 
eminences or processes, rising at regular intervals from the upper circlet or coronet of 
the animal (Plate XXXIII. fig. 1 A); and when the power is feeble from exhaustion, the 
lashing movements of the cilia are very visible. Immediately below the oral orifice 
is a considerable dilatation, closed above by the union of three portions of firm inte- 
gument, forming as it were a labial apparatus, or at least a mechanism for closing the 
mouth, which resembles very closely the visor which conceals the powerful jaws of the 
larvae of the Libellulse. Within the mouth are situated a powerful pair of forcipated 
jaws (Plate XXXIII. fig. 1 E) which seize the prey, and if large comminute and break it 
down. Eacl) ramus of the jaw is jointed (Plate XXXIII. fig. 3) on a short arm, which 
is again moveable upon a central axis prolonged posteriorly; and each short arm has a 
curved and strong process, to which the very powerful and somewhat complicated 
muscles are attached. The forcipated extremities of the jaws are bifid, and may be 
fairly designated teeth, one being sharp and hooked, the other flat or chisel-edged. 
