OF THE MANDUCATORY ORGANS IN THE CLASS ROTIFERA. 
445 
123. Across the uncus, about midway between the bifurcation and the tip, on the 
inferior surface, a membrane orig-inates, which projects transversely and perpendicu- 
larly downwards to some distance, curving- at the bottom towards its fellow of the 
opposite malleus (fig. 80). I incline to think this the vanishing representative of the 
quadrantic mass in Limnias and Rotifer = the ramus of the incus. 
124. The whole apparatus is very minute, and in some specimens can, either not 
at all, or with much difficulty, be detected ; so that we may consider the dental appa- 
ratus of the Rotifera degraded to its lowest point in this genus. 
125. Stephanoceros, the most elegant of Rotifera, affords peculiar facilities for 
observation ; since it is by far the largest animal in the Class, reaching to one-fif- 
teenth of an inch in height*. There are two capacious crops (each bounded by a dia- 
phragm), of which the lower seems to answer to that of Floscularia. The jaws are 
placed in the latter, not in the stomach, which is distinctly separated from it. They 
are evidently imbedded in its dorsal paries, working freely in the cavity, without an 
enclosing mastax'^. 
126. Ehrenberg’s figures of the apparatus seem more than usually incorrect; it 
is but fair to say, however, that he admits his observation to be susceptible of doubt. 
Each malleus is an uncus, of three curved divergent fingers (figs. 84, 85), whose ex- 
tremities are united by an indented membrane, like the foot of a water-fowl. There 
is no distinct manubrium, but the posterior part of the uncus forms a knob, which is 
enclosed in a large muscular bulb. 
127. The incus consists of two very mobile and widely separable rami, somewhat 
quadranti-globular, but much flattened, and each furnished with a lengthened pro- 
cess, which unites with its fellow to form the hinge, without fulcrum (fig. 83). The 
uncus is connected ivith the ramus by an elastic ligament, by which means the latter 
is stretched open vigorously, while the teeth of the malleus act on the prey imprisoned 
in the crop. 
128. Thus I have shown that the masticatory apparatus in the whole class of 
Rotifera is modeled on one common plan. The organs, indeed, are considerably 
modified, and sometimes so much disguised as to be unrecognizable, on cursory exa- 
mination : but a careful scrutiny proves that every modification (for I have omitted 
none, that I am acquainted with, in which there is any variation of importance) is, 
without any violence, referrible to the common type. 
129. This form of the trophi, alone, isolates the Rotifera from other animals, and 
proves, in concurrence with other points of organization, that this class is a very 
natural and well-marked group ; since we find one type of structure running through 
the whole, which is yet widely different from that of any other class of animals. 
130. As no group of animals, however, nor any set of organs, is so isolated as to 
* Ehrenberg can only have seen small specimens, since he mentions one-third of a line as the dimensions 
of the species. I have, however, seen several of the size mentioned in the text. 
d Ehrenberg figures one, indeed, of the usual three-lobed form, but I fear it is imaginary. ' 
3 N 2 
