150 



NATURAL HISTORY 



instead of circular rows; indeed, this animalcule is des- 

 cribed and drawn in this manner in all the old authors — an 

 error which recent improvements in the microscope have 

 demonstrated. This creature, when arrived at maturity, 

 consists of a body in the form of a bell, the edge of which 

 is furnished with a circular fringe of cilia : to the outside 

 of the dome is attached one end of a long pedicle or stalk, 

 and the other is fixed to some extraneous substance. 

 They are gregarious, and their stems are connected in 

 the manner shewn in figure 204, the bells being omitted. 

 When in search of prey, they stretch out the stem, and 

 by means of a vibratory motion communicated to the 

 cilia, they agitate the water and occasion a current 

 towards them, as indicated by the arrows, figure 203 ; 

 this brings along with it the small particles of matter on 

 which they feed. Should any circumstance disturb the 

 water, or a large animal approach them, they instantly 

 retract, bending the stem into a number of coils, as shewn 

 at figure 205 : this operation is performed so quickly that 

 the eye cannot detect it ; in a few seconds, the creature 

 may be observed slowly uncoiling the stem. In some of 

 the larger species, as the F. polt/pina, a muscle has been 

 observed within the stem which assists in this operation.* 

 It has also been asserted that a circulating fluid has been 

 observed in the stems. These curious animalcules are 

 endowed with several methods of propagation, the obser- 

 vation of which has thrown much light upon this in- 



* Transactions of the Society of Arts, Vol. 48. 



