INFUSORIA. 



13 



to shew slight undulations ; the basal extremity of the 

 stem is affixed to the support ; and the bell slowly roams 

 about, with the length of its tether for a radius, now 

 turning its open mouth, now its sides, and now its foot 

 to the eye. 



On any shock, such as a tap with the nail on the stage 

 or " live-box," — instantly, with the quickness of thought, 

 so that the eye can scarcely trace the motion, the long 

 stem is contracted into a beautiful spiral (b), suddenly 

 bringing the bell close to the point of adhesion, when it 

 immediately, but gradually (c), uncoils to its full length. 

 It does not seem alarmed by tapping, except when fully 

 extended ; for it we tap the box all the time it is unfold- 

 ing, it does not shrink again, until it has reached its full 

 extension, but then it does instantly. It frequently, how- 

 ever, springs back again, when partially uncoiled, of its 

 own accord, several times in succession. Hence we may 

 presume that the spiral contraction is the result of alarm ; 

 but that though alarm may be felt from the bell's contact 

 with substances in the water, or from currents, &c, at any 

 time, a shock or tap produces this effect only when the 

 stem is tense, and capable of vibration. The whole of the 

 actions of this little animal are very sprightly and elegant. 



The ordinary increase of the animals of this class is by 

 self-division. In the Vorticellce it takes place in the fol- 

 lowing manner : — One of the full-grown bells begins to 

 alter its form, becoming first globular (6), then a flattened 

 sphere (c), presently a slight notch or depression is observed 

 in the upper part of the outline, and it soon becomes 

 apparent that this depression is a constriction extending 

 all round, which gradually becomes deeper and more 



