raFusoEiA. 453 



■whole surface, on both sides, is covered with minute 

 cilia, arranged in longitudinal rows, of which, accord- 

 ing to the great Prussian professor, there are from 

 thirty to sixty on each surface, each row bearing sixty 

 or seventy cilia. This must be considered as an ap- 

 proximation ; for we may well doubt the accuracy of 

 the counting, when the objects are so very evanescent 

 as these vibrating cilia. 



The vacuoles, and the temporary stomachs, more 

 or less completely filled with the brown and green 

 food, which the animals are collecting from the de- 

 cayed vegetable matters, are sufficiently numerous and 

 conspicuous ; but they may be rendered still more so 

 by the device of mixing a little carmine with the 

 water. The ciliary currents are thus instantaneously 

 rendered striliingly visible. The crimson atoms are 

 attracted from all quarters towards the tail of the ani- 

 mal, whence they are urged in a rapid stream along 

 one side towards the head, around which they are 

 hurled, and then down the other side to the tail, pour- 

 ing ofi" in a dense cloud in a direction contrary to that 

 in which they originally approached. 



But now the gathered currents have produced their 

 expected result ; for many of the globular vacuoles are 

 already become of a beautiful rosy hue, from the mi- 

 nute particles of the pigment which have been whirled 

 to the mouth, and swallowed. 



The feature of greatest interest, however, in tliis 

 animal is the contractile bladder. Two of these organs 

 are usually seen co-existent in each individual ; placed, 

 the one on the front, the other in the rear of the mouth, 

 but near the opposite — i. e. the dorsal, surface of the 

 body ; for as the creature slowly revolves on its longi- 



