176 THE IDEAL PROTOZOAN AND BILATERALITY. 



like a watch-spring, Epistylis and Zoutharnniuin. Yet in all 

 these various degrees of the twist of the spiral, you do not lose 

 sight of the two halves, i. e., its bilaterality. Nor is this alto- 

 gether an ideal transition of degrees of obliquity ; for 

 I have seen one and the same individual assume 

 widely diverse states of this kind, as illustrated 

 in these two figures, (figs. 104 and 105,) --and pass 

 from one into the other whilst I was observing it. 

 When I first saw it, the form was like this, (fig. 

 105,) in which the edge of the disc is drawn out and 

 twisted, (d,) as you would a ribbon, into three or four 

 coils; but gradually this proceeded to unwind, until, 

 in about ten minutes, it had straightened out and projected 

 above the rest of the disc like a broad lip, (fig. 104, d). 



the edge of the bell ; jo, the stem, with a thin thread-like muscle in the axis ; d, 

 the lid-like portion of the disc ; d l , the edge of the disc ; (P, the edge of the disc 

 rolled in ; g, the vestibule of the mouth ; g l , the throat. Original. 



Fig. 105. The same as fig. 104, with the edge of the lid-like part of the disc 

 drawn out and coiled into a spiral; d, the point of the spiral; </, the vestibule of 

 the mouth ; p, the stem. Original. 



