INFUSORIA. 391 



Botifera is connected with a well-defined crystalline lens, 

 whose definite form and high refractive power may in 

 many cases be distinctly marked ; but here nothing of the 

 kind is seen; the spot itself has no certain shape, and 

 does not appear to be bounded by a proper wall. Some 

 forms, which are by general consent admitted to be plants, 

 have similar spots ; and hence it has been, rather too 

 hastily, I venture to think, concluded that they have no 

 connexion with vision. I think it still possible that a sen- 

 sibility to the difference between light and darkness may 

 be the function of the organ. 



I have found that this animal, when allowed to dry on 

 a plate of glass, retains its form and colour perfectly ; but 

 in about two days the eye-spot, which at first becomes 

 much larger in the drying, gradually loses all traces of 

 its brilliant colour, probably by the evaporation of the 

 contained fluid. 



Another pretty species you see gliding along among the 

 rest, called E. triquetra, or the Three-sided. It bears a 

 resemblance to a broad rounded leaf, with the foot-stalk 

 forming a short transparent point, and the mid-rib ele- 

 vated into a sharp ridge. The 

 under side seems slightly concave. 

 This is equally attractive with 

 the others. It is persistent in 

 form, and appears not to be 

 even flexible. Its motion is slow, 

 and as it goes, it rolls irregularly 

 over and over in all directions, THREE . B1DEJ) E „ GI , EKA . 

 not revolving on its long axis, and 



thus giving you very satisfactory views, though only 

 momentary, of the keel with which the back is furnished. 

 It is in the turnings of such minute creatures that the 

 microscopist often gets a glimpse of peculiarities of form, 

 which a view of the animal when in repose, however long 

 continued, fails to reveal. Longitudinal interrupted lines 



