228 Transactions of the Boyal Microsco]pical Society. 
tlie addition of atoms of carmine. Both Melicerta ringens and my 
new rotifer, which I have named Melicerta tyro, have their secre- 
ting gland below a ciliated cup, the cilia doubtless in their case, 
as in that of Pterodina, acting to keep the sticky surface of the 
gland free from constant clogging. But the cup of M. tyro differs 
from that of M. ringens in its not being united by lines of cilia to 
the ciliated chin. In M. ringens two constant streams of very fine 
particles may be seen to trickle through two notches on either side 
of the chin, and to be conducted gently into the ciliated cup 
there to be converted into pellets ; while the larger ones are hurled 
furiously over the ciliated chin. M. tyro has not got these lines of 
fine cilia from the notches in the chin to its ciliated cup, and so all 
the atoms large and great rejected at the mouth fly swiftly off 
together over the chin, and never reach the cup which lies just 
beneath. It is the lack therefore of these special cilia which seems 
to prevent M. tyro from making the same use of its cup that 
M. ringens does. 
The sheath of M. tyro is generally tolerably transparent, and 
like that of all the tube-makers, it is not a hollow cylinder, but 
(if I may use the term) a solid one with a tubular axis of very 
small bore, up and down which the rotifer moves. Viewed as a 
transparent object, it is sometimes difficult to make out the real 
structure of the tube, but with dark-ground illumination and with 
the binocular there can be no doubt about it for a moment. 
The central tube down which the stem of the rotifer passes is 
often widened at the top into an inverted cone by its frequent semi- 
contractions ; and this portion too is often rendered conspicuous by 
the debris of confervse, or by diatoms rubbed off on it by the twisting 
Melicertan. When the creature contracts wholly it does not tend 
to make such a cone ; and as now and then it has fits of complete 
contractions, and afterwards of semi-contractions, so at one time it 
forms a dirty cone at the top of its tube, and at another buries the 
cone with fresh accumulations of evenly distributed viscous secre- 
tions. Thus it happens that as the animal ages and the tube 
grows, tiers of discoloured cones occur one above another ; and all 
of these, as the animal works up and down in its tube, are pushed 
at last into horizontal layers. This is seen in all the figures in the 
Plate, but especially in Fig. 2, in which the layers — the flattened 
surfaces of the discoloured cones — are sprinkled with diatoms. 
The trochal disk acquires its butterfly shape from a habit which 
the creature has of bending the corners of the two top lobes of the 
disk. The four lobes are really all rounded just like those of 
M. ringens, and are often seen fully expanded and round. The two 
antennae are of prodigious length; and, owing to their size and 
transparency, it is easy to see how the muscle that runs up to the 
bunch of seta} at tlie top can withdraw them, by infolding the tube 
