N. E. GREEN ON CILIARY ACTION IN ROTIFERA. 77 



and trying every available power and kind of illumination, we were 

 about to give it up once more, when, wandering over the slide with- 

 out any definite intention, we came upon an unusually fine individual, 

 this time stretched longitudinally, and in steady work. The im- 

 mediate neighbourhood of the ridge was, of course, the part scruti- 

 nised, and again the dance of the indigo was observed, and every 

 now and then, the eye seemed to catch the usual flash-like action of 

 cilia. We had been working with an exquisitely corrected quarter- 

 inch by Dalmayer, and with the usual light transmitted through a 

 quarter-inch achromatic condenser. The former power was ex- 

 changed for a -jjr by Ross, and the condenser adjusted with great 

 care, when, on bringing this power into focus on the further side of 

 the chamber, and then raising it in the most delicate manner, so as 

 just to focus that which lay above the surface, our eyes were feasted 

 on the sight of a row of cilia in active operation. Yes, there they 

 were ! — one, two, three, we could almost count them round a por- 

 tion of the curve ; short, thick-set, directed towards the mouth, 

 and busily engaged producing the current, the cause of which had 

 baffled us so long. The hour was near twelve, and the eyes had 

 been more than once bathed with cold water to enable them to bear 

 the strain, so the gas was turned out, and we prepared to turn in, 

 well satisfied with the result of our four hours' search. 



Since this time we have on several occasions verified the fore- 

 going statement, a careful examination of the same locality having 

 seldom failed to reveal these mysterious hairs. Still, we would de- 

 sire to caution any of our friends, who may wish to see for them- 

 selves, that there are peculiar difficulties in the way of success. It 

 is in vain to try on an individual fresh from a free supply of water ; 

 the action is too rapid, a slide must be kept for some days in order 

 to reduce the energy of movement. Then it must be remembered 

 that the cilia are placed just where it is most difficult to see them 

 (see Plate ix.), and the thickening of the integument or side of 

 the chamber makes it doubly difficult to separate so delicate an 

 object from the side itself. The only available situation, at least 

 in our experience, is that described, viz., the inner surface of the 

 further side. 



But our programme would be incomplete without some reference 

 to that very useful body of cilia which we have termed inspectors, 

 whose duty is to examine the general mass of particles drawn in 

 by the action of the wheels, to select that which is suitable for 



JOURN. Q. M. C. No. 11. g 



