OP THE MANDUCATORY ORGANS IN THE CLASS ROTIFERA. 
4 35 
the extremities of fasciae, that extend to the rami; as the motions of the latter are 
synchronous with twitchings in these bulbs. 
73 . There is a subtile clear membrane stretched over the whole apparatus, but not 
in contact with it ; for it has a slight power of independent contraction and pro- 
trusion. It is of considerable breadth, with a blunt point in the centre, which is 
simple in S. mordax, bifid in S. tremula (fig. 41). As there is no buccal funnel^ tins 
must be the occipital (or rather frontal) margin of the niastax, the teeth being evi- 
dently extruded from beneath it ; there must also be a mental, or inferior, margin, 
but I have not defined it. 
76. Polyarthra differs little from Synchceta in the form of its jaws. The mastax is 
more oblique (fig. 47), its central lobe being much produced, and pointing towards 
the venter. The muscles of the upper portion are so dense (fig. 44) as to shut out 
all sight of the interior, until they are dissolved away by potash (fig. 46). 
77 . The rami are very broad, somewhat square at the base, flat, but much arched 
longitudinally (fig. 47). They open and shut vigorously, with a snapping action, but 
are not protruded from the front; their whole interior edges come into contact. 
78. The mallei are simple, slender, bent rods, apparently without distinct articula- 
tion (fig. 48). During life they are thick, and irregular in oulline (fig. 46), owing, 
doubtless, to their being invested with muscle, as in Synchceta. 
79 . There is a clear vaulted membrane, spreading like a dome over the jaws, when 
viewed vertically (i. e. from the front), which is certainly the paries of the mastax-. it 
has an advancing and receding margin (fig. 49), which is placed considerably towards 
the mental aspect, where the mastax opens at the bottom of a shallow funnel. 
80. From these forms, especially that of Synchceta, the transition is easy to Diglena, 
Eosphora, Albertia, and Furcularia marina. Thus, in Diglena forcipata (figs. 50, 51), 
the incus is a true forceps ; the rami projecting in nearly the same plane as the fuL 
a-um., and the hooked points coming into contact. The edges have a peculiar struc- 
ture, being delicately ridged transversely; while from the terminal points of the ridges 
spring slender setse in a double row, which project so as to oppose those of the other 
ramus. This curious structure I find also in Diglena grandis. The fulcrum is com- 
pressed. 
81. The mallei have nearly straight manuhria, slightly enlarged at the free extre- 
mity, and clubbed towards the joint, where they are invested with thick muscle. The 
uncus is a simple curved piece, so far as its point of attachment to the ramus ; but at 
this point there is articulated to it a stout curved acute spine, which, when the rami 
are closed, crosses its fellow of the opposite uncus, and plays over the setae of the 
ramus (fig. 50), In Diglena grandis there are two spines on each uncus, the one much 
shorter than the other; as there are also in Eosphora aurita. In the latter species 
these tooth-like spines are projectile, as a formidable pair of jaws; and 1 doubt not 
that such is their function in Diglena also, though I have not seen them so used ; 
especially as, in both genera, the ciliated disk is prolonged on the prone surface 
3 M 
MDCCCLVI. 
