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. 



" 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 (fi) . 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 (/^;), 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 cm-ve in the 

 opposite direction, so that on the whole it presents a long, 

 drawn-out sigmoid flexure. The plane of this cmwe 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 Jiagelliim, except 

 when assisting the smaller cilium {fi^) 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 Astasia. 



" The smaller cilium (fi^) 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 {fi) ; 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 



