44 



THE MICROSCOPE. 



it not for the small particles of dirt which have 

 attached themselves to it, the animal is seen as a 

 round mass. By-and-by it slowly extends itself till it 

 reaches the open mouth of the tube ; then the an- 

 terior orifice expands, the circlet of cilia is put in 

 active motion, currents of food-producing water are 

 brought within the action of the cilia, and, all of a 

 sudden quick as lightning the little creature, by 



contraction of its 

 muscular tissues, 

 subsides into the 

 form of a ball, as 

 before. From 

 their habit of living 

 in a sheath these 

 creatures are 

 called Vaginicoltz. 

 The wheel-ani- 

 malcules (Rotiferd) 

 will afford you un- 

 limited amusement 

 and instruction. 

 You will recognise 

 their form from 

 the accompanying 

 figure. We advance a step most decidedly here. The 

 animals that have hitherto come before our notice 

 are of low organisation compared with the Rotifer a. 

 How shall we describe the structure of a Stentor 

 or an Ophrydium ? Imagine an animated mass hol- 

 lowed out into one large general cavity. There 

 is a mouth, with its circlet or circlets of cilia, 

 and a stomach some animal organisms, such as 

 amseba and sponge, have not got so much even as 

 this a contractile vesicle, apparently the rudiments 

 of a circulating system, and two nuclei, which represent 



Fig. 19. Wheel-animal culae. 



