74. THOUGHTS ON ANIMALCULES. 



d, The jaws, armed with teeth. 



e, The digestive organs coloured by a solution of carmine swallowed 



by the animal. The direction of the currents to and from the 

 mouth, occasioned by the ciha around the entrance of the ali- 

 mentary canal, is shewn by the colour. 



/, Four bundles of long internal muscles, by which the body is con- 

 tracted and extended. 



g, An eg^ in the ovisac, containing an embryo, in which the eyes and 

 jaws are discernible. 



A, The tail, or pedicle. 



Of the organs above pointed out, the rotators are 

 those wliich always excite most surprise ; for, notwith- 

 standing what has been stated in explanation of their 

 true nature and action, the inexperienced observer will 

 find it difficult to divest himself of the idea that they 

 actually do move round like wheels, for they appear to 

 revolve continuously in one direction, because one set 

 of the vibratory movements of the rows of cilia is alone 

 perceptible, (see lign. 1, page 35). Each rotator has 

 from fifty to sixty fine cilia, which when vibrating form 

 twelve or fourteen groups: each cilium swings round 

 on its base, producing a motion like the rotation of the 

 human arm. When any colouring matter is introduced 

 into the water, the directions of the currents caused by 

 the cilia are very manifest. Those produced by the 

 rotators are gyratory ; those by the orifice of the mouth 



