OF THE MANDUCATORY ORGANS IN THE CLASS ROTIFERA. 
429 
the Rotifera, are drawn by the discal vortices into the funnel, and lodged at this 
point, within the mastax. The unci, and the rami of the incus, conjointly work on 
them; and they are speedily dismissed to the tips of the rami, immediately below 
which, on the dorsal side of the mastax, the oesophagus opens ip)', a membranous 
tube, capable of great expansion and contraction, but varying much in length and 
diameter in different genera. A current of water appears to be almost constantly 
setting through the funnel, along the rami, in a direction towards their extremities, 
and thence through the oesophagus into the stomach. 
39. In general, the ciliary vortices are sufficient to bring the prey within ihe funnel-, 
but in several genera of the family Euchlanidota, as Metopidia, Colurus, Monura, and 
Stephanops, there is a curious accessory organ, which aids in the capture of prey ; at 
least, I am sure it is so employed in several species of Metopidia. 
40. Thus, in M. acuminata (fig. 1 1), the frontal region is formed by an arched fleshy 
process occipitally, which is approached by a small one at the mental side; and be- 
tween these is the wide entrance of the huccal funnel. The occipital process is pro- 
tected by a horny crystalline plate, forming a segment of a sphere, and when viewed 
laterally taking the appearance of a curved horn. It can be partially protruded and 
retracted, and also bent down to meet the mental lobe. 
41. This apparatus, when the animal is taking food, is kept in vigorous action. A 
strong vortex is produced by the ciliary wheels ; and as the floating atoms whirl by, 
the moveable plate is thrown forward with a grasping motion, the fleshy head being, 
at the same time, protruded ; and, when the lobes are in contact, retracted. This is 
repeated almost every instant, with manifest eagerness and discrimination, the man- 
ducatory apparatus working vigorously all the while. 
42. The same curious organ is frequently employed in another way. It is bent 
considerably downward ; and, as the animal crawls deliberately up and down the 
stems of aquatic plants, it is used to rake and grub among the floccose deposits, the 
minute Diatomacece, &c., that adhere to them. (See fig. 11.) 
43. Taking the structure described in Brachionus as the standard, I now proceed 
to examine how it is modified in other genera. In Euchlanis deflexa (figs. 12 to 15), 
the fulcrum of the incus (h) is thinned off ventrally to a blade-like edge, which is 
minutely jagged, and dilated laterally at the foot. The rami are very large (g), ex- 
panding at the sides in a triangular, pointed form ; and arching across the mastax 
towards the dorsum, where each terminates in an elongated, curved, descending spine. 
The two points approach each other in a forcipate manner. 
44. The rami are crossed at right angles by the four-fingered unci of the mallei, which 
by their motions evidently open the rami ; though these latter do not appear, as usual, 
to be separable to the fulcrum, but to be united into one piece, with an ovate exca- 
vation between them (fig. 14), that does not reach to the fulcrum. 
45. The manubria are more developed than in Brachionus. Instead of the thick- 
ened knob, to which the uncus is articulated, the upper portion of the manubrium 
3 L 2 
