MOLLUSCA. 23 
“Tight as a flake of foam upon the wind, 
Keel upward from the deep, emerged a shell, 
Shaped like the moon ere half her horn is fill’d ; 
Fraught with young life, it righted as it rose, 
And moved at will along the yielding water. 
The native pilot of this little bark 
Put out a tier of oars on either side, 
Spread to the wafting breeze a twofold sail, 
And mounted up, and glided down the billow, 
In happy freedom, pleased to feel the air, 
And wander in the luxury of light.”—-Prtican ISLAND. 
The accuracy of modern research, however, has 
proved this to be but a pleasant fable. ‘The Ar- 
gonaut is a Cuttle-fish, and crawls along the bot- 
tom, like its fellows, by means of its slender, 
flexible, tentacular arms, as represented in the pre- 
ceding engraving, (fig. 2); while the pair that are 
furnished with a broad fleshy disk, have an office 
very different from that of sails, namely, that of 
forming, repairing, and protecting the thin and 
papery shell. (See fig. 3.) Its only swimming. 
power appears to be that which it possesses in 
common with all Cephalopoda, of shooting along in 
a backward direction, by the force of a jet of water 
from the funnel, as shown at fig. 1, where it is re- 
presented as swimming towards the point a. 
Among the TunicaTa there are some singular 
tribes which swim freely in the sea. “The Salpe, 
translucent as their native waters, and often united 
in chains, after a pattern peculiar to each species, 
are driven along the surface with considerable 
quickness by alternate contractions and expansions, 
and by the propulsion they receive from a current 
of water, which is made continually to traverse the 
long diameter of the body, sucked in by the pos- 
terior aperture, and issuing im a stream through 
that on the side of the mouth. Hence the body is 
