INFUSORIA. 397 



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 

 approximation ; 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 tilled 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 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 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 



