INFUSORIA. 403 



middle, terminating below in a kind of nipple to which 

 the stalk is attached, and above in a short wide neck with 

 a thickened rim. This last is highly sensitive and con- 

 tractile ; its inner edge is set round with a circle of 

 vibratile cilia, which, when in full play, produce a pair of 

 small circular whirlpools over two opposite points of the 

 brim. The cilia themselves cannot be distinguished, but 

 their optical expression is curious. At the two opposite 

 points of the circular margin, as seen in perspective when 

 slightly inclined towards the observer, viz., at those points 

 where the cilia, from their position with regard to the 

 eye, would be crowded together, there are seen two dark 

 dashes, representing, doubtless, two ciliary waves, but 

 which have all the appearance of tangible objects, some- 

 times withdrawn, sometimes protruded, and often 

 vibrated with a rapid snatching movement. 



These vases are of the usual appearance in Infusoria. 

 Their substance is the clear transparent colourless sarcode, 

 but it contains within it more or less of the cloudy 

 nebulous matter which we have been lately familiar with. 

 There are several globular vesicles or vacuoles, some ready 

 to imbibe colour from pigment, and others already occu- 

 pied with brown food ; while in each case we see, near 

 the centre of the vase, a longish body of clear granular 

 texture, which is called the nucleus, and which seems to 

 play an essential part in the vital economy of the animal. 



The movements of a group such as that we are looking 

 at are very sprightly and pleasing. The vases turned in 

 all directions, some presenting their mouths, some their 

 sides, some their bases, to the eye ; inclined at various 

 angles from the perpendicular, and bending in diverse 

 degrees upon the extremity of their stalks; swaying 

 slowly and gracefully to and fro, as driven hither and 

 thither by the ciliary currents; and, above all, ever flying 

 up and down within the length of their radius, as a bird 

 when confined by a string ; — all these circumstances 



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