44 THE MICROSCOPE AND ITS REVELATIONS. 



and subsequent drawing-together (somewhat after the fashion of the 

 tentacula of Zoophytes), than of reducing them by any kind of masti- 

 catory process. The curious contraction of the foot-stalk of the Vorticella 

 (Fig. 305), again, is a movement of a different nature, being 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 a leaf or stem of duck-weed ; 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 sud- 

 denly contracts into a spiral, from which it shortly afterwards extends 

 itself again into its previous condition. The central cord, to whose con- 

 tractility this action is due, has been described as muscular, though not 

 possessing the characterictic structure of either kind of muscular fibre ; 

 it possesses, however, the special irritability of muscle ; being instantly 

 called into contraction (according to the observations of Kiihne) by 

 electrical excitation. The only special 'impressionable' organs 1 for the 

 direction of their actions, with the possession of which Infusoria can be 

 credited, are the delicate bristle-like bodies which project in some of 

 them from the neighborhood of the mouth, and in Stentor from various 

 parts of the surface. The red spots seen in many Infusoria, which have 

 been designated as eyes by Prof. Ehrenberg from their supposed corre- 

 spondence with the eye-spots of Rotifera ( 447), really bear a much 

 greater resemblance to the red spots which are so frequently seen among 

 Protophytes ( 230). 



438. The interior of the body does not always seem to consist of a 

 simple undivided cavity occupied by soft sarcode; for the tegumentary 

 layer appears in many instances to send prolongations across it in differ- 

 ent directions, so as to divide it into chambers of irregular shape, freely 

 communicating with each other, which may be occupied either by sar- 

 code, or by particles introduced from without. The alimentary particles 

 which can be distinguished in the interior of the transparent bodies of 

 Infusoria, are usually protophytes of various kinds, either entire or in a 

 fragmentary state. The Diatomaceae seem to be the ordinary food of 

 many; and the insolubility of their loricm enables the observer to recog- 

 nize them unmistakably. Sometimes entire Infusoria are observed within 

 the bodies of others not much exceeding them in size (Fig. 308, B); but 

 this is only when they have been recently swallowed, since the prey 

 speedily undergoes digestion. It would seem as if these creatures do not 

 feed by any means indiscriminately, since particular kinds of them are 

 attracted by particular kinds of aliment; the crushed bodies and eggs of 

 Entomostraca, for example, are so voraciously consumed by the Coleps, 

 that its body is sometimes quite altered in shape by the distention. This 

 circumstance, however, by no means proves that such creatures possess a 

 sense of taste and a power of determinate selection; for many instances 

 might be cited, in which actions of the like apparently- conscious nature 

 are performed without any such guidance. The ordinary process of 

 feeding, as well as the nature and direction of the ciliary currents, may 



1 The term ' organs of sense ' implies a consciousness of impressions, with which 

 it is difficult to conceive that unicellular Infusoria can be endowed. The com- 

 ponent cells of the Human body do their work without themselves knowing it. 



