INFUSORIA. 897 



which are fringed with long cilia, whose vibrations are very 

 marked. The whole surface, on both sides, is covered 

 with minute cilia, arranged in longitudinal rows, of which, 

 according 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 approxima- 

 tion ; 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 decayed 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 strikingly visible. The crimson 

 atoms are attracted from all quarters towards the tail of the 

 animal, 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, pouring off in a dense 

 cloud in a direction contrary to that in which they origi- 

 nally approached. 



But now the gathered currents have produced their ex- 

 pected result ; for many of the globular vacuoles are already 

 become of a beautiful rosy hue, from the minute particles 

 of the pigment which have been whirled to the mouth, and 

 swallowed. 



The feature of greatest interest, however, in this 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 longitu- 

 dinal axis, the line of the vesicles alternately approaches 

 and recedes from that of the mouth. They are remarkable 

 for their structure. Far from the simplicity in which the 



