14 FR1DTJ0F NANSEN. [noew. pol. EXP. 



This colourless space is evidently a vacuole. At the posterior, slightly pointed 

 extremity of the body, I believe I have seen a small opening in the mem- 

 brane of the animal; but I have never with certainty seen anything being 

 pushed out through it". 



"The contents of the cell have the same dark green granular appearance 

 in all these dark individuals. Near the margins single grains can be distin- 

 guished, of the same size and appearance as the oscillating grains seen in 

 Fig. 6, 6". 



"Here and there small colourless vesicles occur, which might be vacuoles 

 if it had not been for their small size — they are not much greater than the 

 dark grains or globules — nor have I seen any contractile movement in them, 

 although they seem to change slowly". 



PL 2, Fig. 5 represents a similar spheroidal, motionless form of dark in- 

 dividual seen on another occasion (July 24, 1894). But here the cilia were 

 apparently longer and more numerous than in most other individuals observed, 

 and no indication of the spirally-wound furrows was to be seen. 



PL I, Figs. 13 and 14 probably represents another but nearly allied spe- 

 cies of this same genus of Infusorium. It was observed on August 2nd, 1894, 

 amongst diatoms from a pond in a floe. In its mobile state (Fig. 14) it was 

 conspicuously more extended and slender than the above described form. 

 "I followed it for a long time, and there was a striking difference between 

 the elegant worm-like movements with which it moved through the narrow 

 passages between the alga?, and those of the thicker form above, in both 

 dark and transparent modifications. It was never seen to contract to a shape 

 approaching that of the latter, and the body seemed to be also more "mus- 

 cular", as the spirally wound furrows became more conspicuous on contraction 

 (Fig. 13). 



After a while, it contracted into the motionless stage; but this did not 

 occur in the same manner as often observed (see description above); it took 

 place more gradually and quietly: It did not run about in long circuits back- 

 wards through the water; the "muscles" were more and more energetically con- 

 tracted, the spirally-wound ribs became more prominent and protruded (Fig. 13). 

 They are possibly somewhat more numerous than in the above form. As in 

 the latter there is a vacuole near the posterior end, and this is conspicuously 

 visible both in the mobile and in the quiescent slate. In its quiescent state 



