32 On Syncheta Mordaz. ee tea 
I have repeatedly watched the same tag and seen it, as it was 
turned over by the animal’s motions, put on either guise: in fact, the 
tag 10,b, is evidently 10, a, seen sideways, and I cannot imagine a 
cilium giving rise to the appearances in 10,a. Besides, the use of 
the cilium is said to be to give rise to currents in the tubes towards 
the contractile vesicle into which they empty themselves. Now how 
could cilia produce currents in capillary tubes of such extreme mi- 
nuteness? Let anyone attempt to blow out water from a glass 
tube tapering to a capillary end, and I think he will doubt of the 
power of a cilium to set up a current in it. There is, however, 
among the multitude of guesses about the water vascular system one 
ascertained fact, and that is, that the contractile vesicle empties 
itself into the cloaca. Cohn states that he has seen the current pro- 
duced in the surrounding water after each contraction, and I have 
myself witnessed it in Brachionus, though I have never seen any 
return current inwards, as Cohn thinks he has. 
If the contractile vesicle were filled from without by a return 
current, the whole apparatus of tags, &c., would be, I think, inexpli- 
cable: but suppose for a moment that Cohn might be mistaken and 
that some valve or construction prevents any return current, it is 
clear that a partial vacuum would be produced in the vesicle by the 
close contraction of its walls on themselves, and if the tubes carry- 
ing the tags opened (as they are generally supposed to do) into the 
vesicle, and the tags had open ends, then the fluid between the viscera 
and the cuticle would be constantly drawn through their apertures 
into the tubes and so into the contractile vesicle ; thence to be ex- 
pelled through the cloaca. 
The rush of fluid through the open ends of the tags, whose true 
shape is, I think, that of a flattened jelly-bag, might cause a quiver- 
ing like that produced by blowing between two pieces of paper nearly 
in contact; and this quivering seen in profile would look like a cilium 
in rapid action with its free end directed from the aperture, for the 
wavy motion would die away as the fluid passed from the aperture 
of the tag into the tube. 
Should this suggestion prove to be correct, the apparatus would 
appear to be of a urinary nature. That it can be for the purpose 
of aérating the fluids of the rotifer’s body with fresh water is hard 
to believe, when the minuteness of the tubes are taken into account, 
and also the fact that the rotifers are constantly swallowing large 
quantities of water. 
I have only to add that I believe that Synchata, like Hydatina, 
secretes a viscid fluid which exudes from the extremities of its 
pincers; and that this summer I have met with one or two speci- 
mens of S. mordax, whose bodies have been rendered quite opaque 
by vegetable organisms (like the individual corpuscles of Spherosira) 
floating in the fluid between the viscera and the cuticle. 
