438 EVENINGS AT THE MICROSCOPE 



directions, but is most beautiful when straight. The front 

 is furnished with a slender thread-like proboscis. This 

 species affords us a good opportunity of observing the red 

 spot which, for convenience' sake, we may still term an 

 eye. It seems to be an irregular oblong vacuole, or ex- 

 cavation in the sarcode, filled with a clear ruby -red fluid. 

 The red spot in the ftotifera is connected with a well- 

 defined crystalline lens, whose definite form, and high re- 

 fractive 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 can have no connection 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 color 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 color, 

 probably by the evaporation of the 

 contained fluid. 



Another pretty species you see 

 THREE-SIDED EUGLENA. 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 elevated 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, 



