MESSRS. HANCOCK AND EMBLETON ON THE ANATOMY OF DORIS. 209 
short, and provided with a thin projecting- inner lip. Immediately behind this is the 
buccal mass, which is strong and muscular, of considerable size, somewhat ovate, 
with the small end forwards ; it is continuous with the channel of the mouth, and 
the oesophagus leads away from its upper and posterior part. 
There are two sets of retractor muscles for the buccal apparatus*; one composed 
of radiating bands, three or four on each side, inserted into the channel to the mouth 
in front, and attached to the skin at the sides of the body behind ; the other consists 
of only two large strong straps, one on each side, having- their insertions at the sides 
of the posterior part of the buccal mass by means of a band which there encircles that 
body, and running a good way backwards to be fixed to the fleshy foot. These two 
sets of muscles acting together will pull backwards the buccal mass, and mouth 
channel, with the external orifice ; if they act separately, of course they will retract 
the parts into which they are respectively inserted. 
A thin layer of numerous delicate parallel muscular bands coats the lateral parts 
of the buccal mass. These bands are attached in front to the channel of the mouth, 
mingling with other fibres of that part, and behind to the circular band that re- 
ceives the attachment of the buccal retractors. When the channel of the mouth is 
fixed, these layers of muscle will advance the buccal mass towards the external 
orifice. 
The remaining muscles, which are proper to and form nearly the whole of the 
buccal mass, are for the movements of the tongue and the buccal lip, and enclose, 
immediately, the cavity of the mouth. 
On opening the buccal mass-f- from above, by cutting through the buccal lip and 
a strong layer of transverse bundles forming the posterior part of the roof of the 
buccal cavity, and therefore assisting in prehension and deglutition, we see project- 
ing upwards and forwards from the floor of the cavity a broad conical mass sur- 
mounted by rows of teeth, and placed directly in front of the opening of the oeso- 
phagus ; this mass is that of the lingual muscles supporting and moving the spiny 
tongue. In advance of this mass is a powerful sphincter or circular belt of muscle 
commanding the entrance to the mouth ; this we propose to call the third or buccal 
lip, for reasons to be afterwards given. 
The tongue consists of a tubular, dentigerous membrane, the upper or anterior 
portion of which is partly enclosed within, and partly expanded upon, the conical 
mass of lingual muscles ; the lower or posterior portion is continued downwards and 
backwards, through the centre of the mass, into a delicate pouch which projects be- 
yond the posterior and under part of the buccal organ. This spiny tongue:|: is easily 
detached from the muscular mass to which it is connected, and can be drawn out of 
the tube in which it is lodged ; and it can then be observed that the part of the mus- 
cular mass§ which has been covered by the tongue is composed of numerous parallel 
transverse plates or flakes corresponding apparently in number and direction to the 
rows of teeth. These flakes are bound together by a thin layer of fibres which crosses 
* Plate XIII. fig. 1. -{• Plate XIII. fig. 2. % Plate XIII. fig. 3. § Plate XIII. figs. 4 and 5. 
2 E 2 
