LIMPETS. 151 
tongue of the Limpet, and not at any intruder into 
the privacy of his conical fortress.” * 
This curiously toothed tongue ‘is never pro- 
truded beyond the margin of the lips. It seems to 
be used for rasping down the food; and in pyro- 
portion as the anterior prickles are worn away in 
this operation, and absorbed, another portion of the 
tongue is brought forward to supply its place; but 
that there may be no deficiency in its length, we 
find the apex soft and vascular, where in fact 
a continual growth and addition are going on. 
‘“‘ When a phytophagous Gasteropod is about to 
eat, it thrusts forward, and to a certain extent, 
evolves, the spinous tongue, protruding at the same 
time the lip on each side, by which the tongue is 
compressed and forced into the form of the bowl of 
a spoon. The food is now taken hold on by the 
lips, drawn forwards, and retained by the prickly 
tongue, and simultaneously pressed against the 
upper horny jaw, by which means a portion is 
bitten off, sometimes with a very audible noise. 
The detached morsel is then passed along the 
tongue, torn and rasped down by its sharp prickles, 
and forced on by the peristaltic motion of the organ, 
and by the retropulsive action of the adjacent 
muscles, the mass is made to enter the gullet. At 
the entrance of this canal, there is an uvular ca- 
runcle, which is probably the seat of the animal’s 
taste ; and on its side a pair of lobulated salivary 
glands, or sometimes two pairs, which have each 
a single excretory duct to convey their peculiar 
secretion into its upper part, to lubricate and soften 
the mass. The gullet is a muscular canal, lined 
interiorly with a mucous coat, presenting, indeed, 
* Introduction to Zool. i. 178. 
