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* 
as Infusoria flagellata. 211 
above is attached close to the mouth (m), and invariably curves 
away from the beak, and consequently always towards the 
pedicel ( pd) of the colony.” ) 
¢ Prehensile organs.—The only motile organs which this 
animalcule possesses are preeminently prehensile in character; 
and their apparent appropriation to the office of propulsion, 
when a colony breaks loose from its attachment, I can scarcely 
doubt is an accidental one, inasmuch as the arcuate cilium 
continues its spasmodic twitching without any apparent devia- 
tion from its usual mode of action. | 4 
_ “There are two cilia, of very unequal size, attached to the 
truncate end of the body. The larger one of these has already 
been mentioned casually, as a rigid, arcuate filament (fl). It 
does not taper, but has a uniform thickness from base to tip, 
and is about half as long again as the body. It arises near 
the base of the triangular beak (/p), but appears to be separated 
from the latter by the intervening mouth (m). When quiet, 
it appears like a bristle, and projects in a line with the longer 
axis of the body—at the base bending slightly toward the beak, 
and then sweeping off in a moderate but distinct: curve in the 
opposite direction, so that on the whole it presents a long, 
drawn-out sigmoid flexure. The plane of this curve lies in 
strict parallelism with the plane of the greater diameter of the 
body ; in fact it may be said to be a direct continuation of it. 
It does not appear to have the character of a flagellum, except 
when assisting the smaller cilium (//') to convey the food to 
the mouth; and then it lays aside its rigid deportment, and 
assumes all the flexibility and wavy vibration of the prehensile 
organ of an Astasva. | 
“ The smaller cilium (fl!) is an excessively faint body, and 
almost defies the detective powers of the highest objectives. 
This is partly due to its almost incessant activity ; for when it 
is quiet or nearly so (which happens when food is passing into 
the mouth), it becomes comparatively quite conspicuous under 
a one-eighth-of-an-inch objective. It is scarcely as long as the 
greater diameter of the truncate end of the body. It arises close 
to the base of the larger cilium (1); but whether on the right or 
left, or nearer or more distant from the mouth than the latter, 
cannot be said positively. Most frequently it was observed to be 
flexed in the same direction as its companion ; and occasionally 
‘it seemed to be quite evident that it was attached nearer to the 
mouth than the latter. It is highly flexible, and vibrates with 
great rapidity in what appears to be a gyratory manner. 
“‘ The mouth—This organ is never visible except when 
food is passing through it (figs. 50,51,m). It then may be 
seen that it lies close to the beak, which acts as a sort of lip 
