74 N. E. GREEN ON CILIARY ACTION IN ROTIFERA. 



rapid in the anterior row, that the fringe itself disappears, and 

 what is usually seen at the margin of the cup is simply a vibratory 

 movement of the stouter hairs of a second or posterior series. 



We cannot leave this subject without referring to a charming 

 scintillating movement, observed in Conochilus volvox, when the 

 action is ceasing ; it results from an energetic stretching out and 

 momentary rest of each cilium, when at that part of its action 

 furthest from the centre. The effect of this momentary rest is to 

 produce a radiating and progressive scintillation, the beauty of 

 which is beyond the power of description, and must be seen in 

 order to be appreciated. 



During these examinations we frequently observed a duplicate 

 arrangement of the cilia forming the wheels ; this first attracted 

 notice in the vorticella, for when their movements became languid 

 an inner and an outer row were clearly seen; the inner long and 

 close set, extending from the bell like a silken fringe ; the outer 

 fewer in number, stouter in form, and radiating from the centre. 

 It was also evident that the two rows were not always in action at 

 the same time, for in some instances a movement in the inner circle 

 preceded that of the outer, and in several instances the inner was 

 observed in slow action, while the outer remained stationary. We 

 have already remarked that the peculiar appearance at the margin 

 of the cup seems to be due to a vibratory movement of this outer 

 series, and a careful examination will make this evident, for the 

 extremes of action are marked by a ghost-like cilium, and between 

 these there may be observed a faint fan-like cloud, produced by 

 the passing and re-passing of the cilium over the intervening 

 space. This movement is evidently very different from that of the 

 wheels. Truly wonderful is the power possessed by this atom, 

 feed it with a little indigo, and observe the vortex formed by its 

 action ; the particles are drawn in on all sides as by a maelstrom, 

 while a long stream of rejected matter is thrown off like smoke 

 from a steam tug. May not part of this amazing energy be ac- 

 counted for by the united action of the two fringes of cilia, the 

 anterior drawing in, while the posterior drives off in all directions? 



But to proceed. We have observed this double series or some 

 modification of it in Stentor, Brachionus, common Rotifer, Philo- 

 dina, Vaginicola, &c, and in a former paper mention was made of 

 a similar series in Melicerta. In the common Rotifer, Philodina, 

 and Brachionus, the second series is placed under a fold of the 



