46 VIEWS OF THE MICROSCOPIC WORLD. 



These singular creatures are found in the red sediment left in gutters and 

 troughs, after the rain-water contained in them has evaporated ; also in vegetable 

 infusions, especially that of hay ; and they likewise swarm in great abundance in 

 ponds covered with water-plants. In sea-water they are also detected, and it is 

 said that they have even been observed moving freely in the cells of terrestrial 

 and marine plants. 



The wheel-animalcule enjoys the sunshine, and can seldom be taken in a cloudy 

 day ; for then it seeks the bottom of the water, lurking around the roots of 

 the weeds that grow therein. When the small pools in which they reside have 

 been reduced by evaporation, they become so numerous as to tint the water with 

 a bright red. They have then attained their full size, and the richness of their 

 hue is at its height ; but if they are now confined in a vessel for a few days, their 

 color fades entirely away. Pritchard remarks that he had found wheel animals, 

 taken under the circumstances just detailed, to measure one-thirtieth of an inch 

 in length ; while those raised in artificial infusions seldom exceeded half that size. 

 They were so numerous that thirty were contained in a single drop. He also 

 observes, that they are easily preserved for a long time, by occasionally placing 

 a little hay in the water of the glass vessel in which they live. He was enabled 

 in this manner to keep them for the space of five years ; and the drawings we 

 shall now describe are representations of specimens preserved. The wheel-ani- 

 malcules are mostly seen under the forms delineated in figures 59 and 60 the 

 first of which represents a full-grown animalcule, and the second the same when 

 young. The double cup-shaped, wheel-like organs are seen at c?, d, in figure 59, sur- 

 mounting the head of the creature, and are each furnished with circles of cilia, 

 apparently in constant rotation ; causing currents, as shown by the arrows, to 

 set towards the opening between the wheel, bearing along the particles of matter 

 upon which they feed. From this opening the food is carried through the neck, 

 m, (the position of which is indicated by a dark line) to the mouth, Z, situated 

 at the bottom of the neck. These curious organs are more clearly displayed in 

 figure 7, where not only the crowns of cilia, but the jaws, teeth, and eyes, are de- 

 lineated as they appear when very highly magnified. Here the rotatory organs are 

 seen consisting each of twelve or fourteen groups of cilia, which, swinging round 

 upon their bases, describe small conical surfaces, terminated by the dotted circles. 

 The animalcule is endowed with the power of changing the direction in 

 which the wheels appear to revolve, and also of instantly drawing in the whole 

 of its wheel work. The head then assumes the form presented in figure 61, 

 where it is terminated by a cluster of hairs that do not revolve. This tuft is re- 

 garded as a set of filaments distinct from those that encircle the wheel-organs ; 

 and which are supposed to perform the office of feelers, as they are usually pro- 

 truded when the animal is moving from place to place. Near the head, and at 

 the upper part of the tube through which the creature receives its food, are four 

 muscular masses of a hemispherical form, placed opposite to each other, as shown 

 in figure 7. Two of the masses are furnished with jaws and teeth ; the 

 jaws are semi-circular in form, and are each armed with two teeth, that are in- 



