222 Mr. Faraday on a 



circularly as long and as often as he pleases by the articula- 

 tion of a ball and socket, may not there possibly be some sort 

 of articulation in this creature whereby its wheels or funnels 

 are enabled to turn themselves quite round ? 



' It is certain all appearances are so much on this side the 

 question, that I never met with any who did not, on seeing it, 

 call it a rotation; though, from a difficulty concerning how it 

 can be effected, some have imagined they might be deceived. 

 M. Leeuwenhoek also declared them to be wheels that turn 

 round, vide Phil. Trans., No. 295. But I shall contend with 

 nobody about this matter : it is very easy for me, I know, to 

 be mistaken, and so far possible for others to be so too, that I 

 am persuaded some have mistaken the animal itself, which 

 perhaps they never saw ; whilst, instead thereof, they have 

 been examining one or other of the several water-animalcules 

 that are furnished with an apparatus commonly called wheels, 

 though they turn not round, but excite a current by the mere 

 vibration of fibrillce about their edges.' 



Notwithstanding the evidence adduced by Mr. Baker, which, 

 as I have said, is admitted by some at the present day, it must 

 be evident, from a consideration of the nature of muscular 

 force, and the condition of continuity under which all animals 

 exist, that the rotation cannot really occur. The appearances 

 are altogether so like some of those exhibited in the experi- 

 ments already described, that I feel no doubt the wheels must 

 be considered not as having any real existence, but merely as 

 spectra, produced by parts too minute, or else having too great 

 a velocity when in use by the animal to be themselves recog- 

 nized. It is not meant that they are produced by toothed or 

 radiated wheels ; for that supposition would take for granted 

 what has already been considered as impossible continual 

 revolution of one part of an animal whilst another part is fixed; 

 but arrangements may be conceived, which are perfectly 

 consistent with the usual animal organization, and yet com- 

 petent to produce all the effects and appearances observed. 

 Thus, if that part of the head of the animal were surrounded 

 by fibrillae, endowed each with muscular power, and project- 

 ing on all sides, so as to form a kind of wheel ; and if these 

 fibrils were successively moved in a tangental direction rapidly 



