INPUSOKIA, THEIR MOVEMENTS. 415 



cases, the filaments are comparatively short, and have a bristle- 

 like firmness ; and instead of being kept in vibration, they are 

 moved (like the spines of Echini) by the contraction of the sub- 

 stance to which their bases are attached, in such a manner that 

 the animalcule crawls by their means over a solid surface, as we 

 see especially in Trichoda lynceus (Fig. 199, p, q). In Chilodon 

 and JVassula, the mouth is provided with a circlet of these bristles, 

 which have received the designation of " teeth ;" their function, 

 however, is rather that of laying hold of alimentary particles by 

 their expansion and subsequent drawing together (somewhat 

 after the fashion of the tentacula of Zoophytes), than of reducing 

 them by any kind of masticatory process. 



268. The modes of movement which Infusory Animalcules 

 execute by means of these instruments, are extremely varied 

 and remarkable. Some propel themselves directly forwards, 

 with a velocity which appears, when thus highly magnified, like 

 that of an arrow, so that the eye can scarcely follow them, whilst 

 others drag their bodies slowly along like a leech. Some attach 

 themselves by one of their long filaments to a fixed point, and 

 revolve around it with great rapidity, whilst others move by 

 undulations, leaps, or successive gyrations ; in short, there is 

 scarcely any kind of animal movement which they do not 

 exhibit. There is no sufficient reason, however, to regard such 

 actions as indicative of consciousness; indeed, the very fact 

 that they are performed by the instrumentality of cilia seems to 

 imply the contrary; since we know that ciliary action takes 

 place to a large extent in our own bodies, without the least 

 dependence upon our consciousness, and that it is also used as a 

 means of dispersion among the zoospores of the lowest Plants, 

 which cannot for a moment be supposed to be endowed with this 

 attribute. We can only regard it, therefore, as indicative of a 

 wonderful adaptation, on the part of these simple ciliated cells, 

 to a kind of life which enables them to go in quest of their own 

 nutriment, and to introduce it, when obtained, into the interior 

 of their bodies. The curious contraction of the footstalk of the 

 Vorticella, however, is a movement of a very difterent nature, 

 and is due to the contractility of the tissue that occupies the 

 interior of the tubular pedicle. This stalk serves to attach the 

 bell-shaped body of the Animalcule to some fixed object, such as 

 the leaf or stem of duckweed ; and when the animal is in search of 

 food, with its cilia in active vibration, the stalk is fully extended. 

 If, however, the Animalcule should have drawn to its mouth any 

 particles too large to be received within it, or should be touched by 

 any other that happens to be swimming near it, or should be 

 "jarred" by a smart tap on the stage of the microscope, the stalk 

 suddenly contracts into a spii-al, from which it shortly afterwards 

 extends itself again into its previous condition . The centi'al cord to 

 whose contractility this action is due, has been described as muscu- 

 lar; but it does not possess the characteristic structure of either 



