MR. T. H. HUXLEY ON THE MORPHOLOGY OF THE CEPHALOUS MOLLUSCA. 31 
to the left of the male, but a long cylindrical egg-tube frequently trails from the 
aperture of the oviduct (fig. 2). 
Alimentary System. — This consists of, — 1, the buccal mass ; 2, the oesophagus and 
stomach ; 3, the intestine and its termination, the rectum ; 4, the liver ; and 5, the 
salivary glands, which are very small and placed above the buccal mass, contrasting 
singularly with the very large salivary glands of Atlanta. 
The oesophagus, stomach, and intestine form a straight tube running through the 
axis of the animal, and suspended by a ligament to the dorsal parietes (fig, 1) ; having 
reached the nucleus,” that is, the mass of the liver and ovary, the intestine bends 
up at a right angle, and so becomes the rectum, which terminates, as has been seen, 
upon the dorsal surface. 
The Buccal Mass, or Tongue (fig. 1 b). — This is an oval brownish body, placed 
below the commencement of the oesophagus, and forming the floor of the cavity of 
the mouth. The following parts may be distinguished in this mass : — 
1. Two ovoid compressed masses of thick -walled clear cells, which somewhat 
resemble cartilage. I shall call these the lingual cartilages.” 
2. These give attachment to muscular fibres by their outer surface, and are enve- 
loped in them. One portion of these fibres is inserted anteriorly into the parietes 
of the body, and acts therefore as a protractor. The rest are inserted into the edges 
of a thin plate, the “ tongue-plate,” which is closely applied to the whole of the upper 
and a part of the anterior lower surface of the cartilages, being as it were bent over 
their anterior extremities. The applied surfaces of the plate and of the cartilages are 
perfectly smooth, so that the former can play readily over the latter, like a rope upon 
its pulley. The upper surface of the tongue-plate carries in the middle a single row 
of tridentate teeth ; outside these is a row of conical spines and broad flat-edged 
plates, and most externally there are one or more rows of recurved hooks, which, 
when the organ is at rest, lie over and nearly meet one another in the middle line. 
When this organ is in action, it is commonly more or less protruded from the mouth 
by the protractor muscles ; the large lateral spines of the tongue are divaricated 
(giving rise to that resemblance to the oral armature of Sagitta which has been 
remarked), so as to get all the teeth to bear ; and then by the alternate action of the 
upper and lower sets of muscles inserted into the tongue-plate, a chain saw-like 
movement is communicated thereto, in consequence of which the teeth act as a rasp 
or saw upon any body with which they are brought in contact. 
The buccal cartilages take no part in the movement of the tongue-plate, but 
simply act as its pulley. 
The GEsophagus widens so gradually into the stomach, that no distinct line of 
demarcation can be drawn between the two, but the latter narrows suddenly into the 
intestine at a short distance in front of the ‘‘ nucleus.” 
The Liver (/) is composed of several foliaceous masses containing many oil-globules ; 
it opens by a wide duct into the angle of junction of the intestine and rectum. 
