5 SO 



THE VORTICELLA. 



Two species of Infusoria, termed Vorticella citrina and Stentor polymorphis, may be found 

 in soft water that has been allowed to remain in the open air, and in which any vegetable 



matter has been permitted to decay. Both 

 these creatures are affixed by footstalks to 

 some object on which they make their resi- 

 dence, and both agree in having a bell-like 

 mouth, edged with a fringe of cilia. 



These organs are set upon the edge of the 

 mouth, and their object is indirectly to draw 

 food into the system by creating certain cur- 

 rents in the surrounding water. When the 

 cilia are exposed to a good microscope, they 

 appear to be formed like the cogs of a little 

 wheel, which is rotating with great rapidity ; 

 and it is not until a close examination de- 

 tects the real cause of this appearance that its 

 illusory nature is discovered. As in the case 

 of the cilia attached to the higher animals, of 

 which a notice has already been given, each 

 fibril bends in regular succession, so as to pro- 

 duce the effect of waves upon the eye. 



When the Infusoria are free, the continual 

 movement of the cilia causes them to move 

 with greater or lesser swiftness through the 

 water, each fibril acting as a minute paddle, 

 and having a distinct feathering movement, 

 like that of an oar handled by a skilful rower. 

 It is a most curious sight to observe the ad- 

 mirable manner in which they make their 

 strokes, the flattened sides striking the water 

 so as to give the greatest force to the blow, 

 and the back stroke being made with the edge, 

 so as to meet with the least possible resistance. 



In the VOBTICELLA, the footstalks on 

 which the bell-like cup is seated are of consid- 

 erable length, and capable of being shortened 

 by being coiled into a spiral form. This is by 

 no means an uncommon Inf usorian, and is very 

 liberal in displaying this capability. It is 

 usually found associating in groups, so that 

 there is hardly a stage in its life of which 

 some example cannot be discovered. Though 

 devoid of apparent organs of sense, this nv:i- 

 ture is marvellously timid, shrinking in a 

 moment if the water be shaken, and tighten- 

 ing its coils until they resemble the spiral 

 rings of a vine's tendril. It soon, however, 

 recovers itself, and by stow degrees permits 

 the spires to uncoil, and waves its fringed 

 head boldly in the narrow prison to which it 



has been consigned. Sometimes the Vorticella breaks away from its footstalks, and is then 

 carried rapidly through the water by the action of its ever- waving fringe of cilia. 



As is the case with many of its kindred, the Vorticella is able to increase its numbers by 

 the simple process of splitting itself into two distinct beings, each of which is afterwards a, 



STENTOR. Stentor polymorphb. (Two hundred times enlarged). 



