130 The Microscope. 



might not unnaturally expect, that the difficulty of 

 understanding how the rotation could be contrived, 

 ' ' hath caused many people to imagine that there was 

 a deception in the case;" and it is interesting to 

 observe how those incredulous people in due time 

 have arrived at the truth. 



The singular organ, A, is variously known as the 

 gizzard, masticating apparatus, jaws, and mouth. 

 It is to be observed, especially when the rotifer 

 fixes itself by its tail-foot and puts its " wheels" 

 into motion, working away actively as if grinding 

 the food; and, no doubt, it is thus employed. It 

 works with a peculiar force and smoothness, re- 

 minding the beholder of the movement of well-oiled 

 machinery. This organ is characteristic of the 

 rotifers; all possess this, though the wheels are by 

 no means universal among them. 



Dr. Carpenter divides the Rotifera into four 

 groups, which I shall name, having been fortunate 

 enough to meet with specimens of each. He follows 

 the division propounded by M. Dujardin, which is 

 based on the several modes of life of the different 

 rotifers. For some always continue attached by the 

 foot to a leaf or other permanent resting-place ; 

 others can thus attach themselves, but are also able 

 to move, leech-like, or by rowing themselves by 

 means of their cilia through the water ; a third group 

 habitually swim, and rarely attach themselves ; while 

 a fourth creep slowly, and indeed seem to resemble 

 Rotifer vulgaris in little except the possession of some- 

 what similar jaws. 



