OF THE MANDUCATORY ORGANS IN THE CLASS ROTIFERA. 
443 
a typical species, consists of the usual three globose lobes, of which the two lateral 
are somewhat produced above, to embrace the termination of the funnel. The dental 
apparatus differs very little from the type which we have seen in Limnias and its 
fellows. The mallei and the incus are soldered together, into two sub-quadranti-glo- 
bular masses (^), which appear to be muscular, but invested with a solid integument. 
These contain the rami of the incus^ and are crossed by two strong teeth, which rise 
from below the exterior edge of the mass, and descend upon its interior face. 
113. The manuhria are more obsolescent than in Limnias-, but they may still be 
recognized, in a vertical aspect (fig. 74), as three loops, of which the central one is 
chiefly developed (c); and in a dorsal aspect (fig. 72), as a translucent, reniform lobe, 
descending on the exterior of each quadrant. Numerous delicate striae cross the qua- 
drantic masses, on each side of the principal teeth, and these are permanent (fig. 74) 
after potash-treatment. A very minute and rudimentary /w/crwm (fig. 75? h') is seen 
in the lateral aspect. 
114. The structure and action of an apparatus of this type may be made more 
clear by a homely illustration. Suppose an apple to be divided longitudinally, leaving 
the stalk attached to one half. Let this now be again split longitudinally, so far as 
the stalk, but not actually separating either portion from it. Draw the two portions 
slightly apart, and lay them down on their rounded surfaces (fig. 76)- They now 
represent the quadrantic masses in repose, the stalk being the f ulcrum, and the upper 
surfaces being crossed by the teeth. By the contraction of the muscles of which 
they are composed, the two segments are made to turn on their long axes, until the 
points of the teeth are brought into contact, and the toothed surfaces rise and 
approach each other (fig. 77 )- The lower edges, however, do not separate, as the 
upper edges approach, but the form of the masses alters, becoming more lenticu- 
lar ; so that when the toothed surfaces are brought into their closest approximation 
(fig. 78), the outline has a subcircular figure. It is on account of this change of form, 
that I presume the masses themselves to be partially composed of muscle. 
115. In Philodina (e. g. P. roseola and P. megalotrocha) the quadrants are con- 
nected by an elastic ligament, which crosses from the interior face of one to the other, 
just below the points of the teeth. I find no trace of this in Rotifer. The teeth are 
generally but two ; in P. aculeata, however, I find, as Ehrenberg does, three, and he 
indicates the same number in P. macrostyla and Monolahis conica, species which I 
have not met with. 
116. It has been usual to call the divisions of the dental apparatus, in this family, 
“stirrup-shaped;” but this comparison is grounded on a misapprehension of their 
true form, which I have proved, by numberless examinations, to be that of the qua- 
drature of a sphere, as above explained. 
117. It is no less evident that Mr. Huxley’s remark, above cited, that the jaws in 
Lacinularia {=Limnias) are “very different from the true stirrup-shaped armature” 
(so-called), is founded on error; the two forms bearing the very closest analogy, as 
3 N 
MDCCCLVI. 
