ROTATORIJE, 335 



seen with their cilia in active vibration. Ehrenberg 

 accurately described the upper part of a common wheel-ani- 

 malcule, with the cilia, jaws, teeth, eyes, &c., as seen under 

 a magnifying power of 200 diameters, and represented in 

 fig. 186, No. 1. The small arrows indicate the direction of 

 the currents produced by the cilia b, turning on their base. 

 At the will of the animal a change is made in the direction 

 in which the wheels appear to revolve, these it has the 

 power of withdrawing, with the quickness of thought ; a 

 cluster of hairs appears at the extremity, that do not 

 revolve, and certainly differ from the cilia : as they are 

 usually protruded when the creature is moving from place 

 to place, their function has been imagined to be that of 

 feelers. 



The red spots, at one time believed to be the eyes of the 

 Rotatoria, are generally of a bright red colour; and the 

 number and arrangement of these organs vary. In some 

 species there have been discovered as many as eight, often 

 placed on either side of the head, in a row, circle, 

 or cluster, and in some they take a triangular shape. 

 The Rotatoria delight in the sunshine; and when the 

 bright luminary is hidden behind clouds, the animals 

 sink to the bottom of the water, and there remain. 

 When the water of their haunts is becoming much evapo- 

 rated, they rise to the top, and give a bright-red tint to 

 it; but when caught and placed in ajar, their beautiful 

 colour fades in a few days. Locomotion is performed by 

 swimming, the rotatory action of the crowns of cilia im- 

 pelling it forward; in other instances it bends its body, 

 then moves its tail up towards the head, with the two 

 processes that serve as feet near the tail ; it then jerks its 

 head to a further distance, a|ain draws up its tail, and so 

 proceeds on its journey. Another peculiarity is that 

 of drawing in the head and tail until nearly globular, 

 and remaining in this condition fixed by the sucker; at 

 other times they become a complete ball, and are rolled 

 about by every agitation of the water. 



The body of the wheel-animalcule is of a whitish colour; 

 its form is indicated in the engraving. The tube for 

 respiration appears to allow of water passing to the inside. 

 On the food being drawn by the currents to the cup part 



