STRUCTURE OF WHEEL- ANIMALCULE. 321 



own food, as soon as they quit the body of the parent. Besides the 

 longitudinal muscular bands, we observe transverse lines crossing 

 the body at intervals, which might be supposed to possess the 

 same character, and to contribute to the elongation of the body 

 by contracting upon the contents of the visceral cavity. Nervous 

 ganglia are suspected to exist in this animal in the neighbour- 

 hood of the eyes ; but they cannot be seen in this species as dis- 

 tinctly as in some other Rotifera. 



930. This animalcule, from the activity of its habits, and 

 the variety of the movements it performs, is one of the most 

 interesting objects which commonly present themselves to the 

 microscopic observer. Sometimes it fixes itself by its forked 

 tail to some solid basis, and then sets its wheels (as they appear) 

 into rapid revolution ; at the same time bending its flexible body 

 in various directions, so as to create currents in different parts 

 of the surrounding water. In this manner it draws into its 

 gullet the unfortunate Animalcules which have been affected by 

 the whirlpool it has created ; just like (it has been amusingly 

 remarked by Spallanzani) a certain species of Whale, which, after 

 having driven herrings into a bay or strait, by a blow of its tail 

 produces a whirlpool of vast extent and great rapidity, which 

 precipitates them down its open mouth. The food thus taken 

 in passes at once towards the stomach, and is submitted to the 

 action of the jaws at its entrance, by which it is broken down. 

 By keeping a Wheel- Animalcule for a few days in pure water, it 

 will become almost perfectly transparent in every part, and its 

 alimentary canal will be completely emptied. If some water 

 containing the green or red Cercarice, or any other small coloured 

 animalcules, be then added, its voracity will be very amusingly 

 exhibited. They will be very distinctly seen passing into the 

 alimentary canal, as fast as the animal can masticate them ; and 

 this will become distended with their coloured substance. It 

 cannot be questioned that the ciliary movement is here entirely 

 subject to the will of the animal. When satisfied with the sup- 

 ply of food it has obtained, the movement of its wheels no longer 

 continues ; and the lateral projections on which they are situated 

 then usually fold themselves inwards, so as to conceal them. 



