IXFL'SORIA. 



.391 



Rotifera 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 sensibility 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 be- 

 comes much larger in the drying, gradually loses all 

 traces of its brilliant colour, probably by the evapora- 

 tion of the contained fluid. 



Another pretty species you see gliding along among 

 the rest, called E. triqrietra, 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 

 elevated into a sharp ridge. The 

 under side seams slightly con- 

 cave. 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, 

 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 



THBEE-SIDED EVGLENA. 



