Characteristics of Rotifers. 



291 



The transition from strongly vibratory cilia to the more 

 quiescent cilia belonging to the Floscularia and Siephanoceros 

 seems abrupt, if we turn immediately from active wheel-cilia to 

 the latter forms, but an attentive examination of rotifiers will 

 often reveal cilia acting so gently as to bridge over the diffe- 

 rence of the two kinds, and probably if the long quiescent cilia 

 were strongly agitated by any force applied to their proximate 

 extremity, that is, to the end which is inserted in the animal, 

 they might execute the wave motions of the other sort. 

 The particles composing wheel-cilia must be in a state of 

 strong tension, and this would seem to result, not from a mere 

 mechanical arrangement, as in a piece of whalebone or a 

 steel spring, but from a cause which ceases with the life of the 

 creature. As soon as a Gonochilus, for example, is dead, its 

 ciliary wreath falls together, in a comparatively soft-looking 

 and inert mass. On the other hand, cilia less distinctively 

 associated with voluntary motion continue their action when 

 torn away from the organism of which they formed a part. 



After the wheel-organs of rotifers, their so-called " giz- 

 zards" are their most striking features. These remarkable struc- 

 tures were very imperfectly known until Mr. Gosse communi- 

 cated to the Royal Society his admirable papers on the subject. 

 Mr. Gosse employed a solution of caustic potash to dissolve — 

 which it does instantly — the soft flesh of the rotifers, and then 

 was able to obtain the manducatory apparatus or gizzard in a 

 separate form. By managing the screws of his compressorium so 



i « 4 



Jk—hr 



FiG. 4. — Mastax of Notornmata 

 clavulata (Grosse). 



as to create water currents, he 

 caused those organs to revolve 

 in various directions, and with 

 wonderful patience and skill 

 Figs. 1, 2, and 3.— Mastax of Brachionus made out details of structure 

 urceolaris (G-csse). anc [ principles of action which 



had escaped previous observers. Mr. Gosse regards the giz- 

 zard as a true mouth, and he calls the muscular bulb contain- 

 ing the biting and grinding machinery a mastax. In Bra- 

 chionus urceolaris and some of the Hydatina he finds the ap- 



