MOLLUSCA. 173 
This gland is supplied by a large branch of the glandular 
aorta, and gives out two very large veins to the left vena 
cava. The fluid itself has never been carefully investigated. 
It is not altered by the air after drying, nor is its colour de- 
stroyed by acids or alkalis, although the tint is a little 
changed, and rendered less pure. Both these reagents pre- 
cipitate white flakes from the fluid. This liquor is poured 
out by the animal when in danger or constrained, and co- 
lours the water for several yards around. It ejects it readily 
when put in fresh water; and when entangled in a net, se- 
veral yards of it in the neighbourhood are sometimes stain- 
ed, greatly to the amazement of the unsuspecting fishermen. 
The Aplysia has been long known in the records of su- 
perstition under the name of the Sea Hare. Its flesh, and 
the inky fluid it pours out, have been regarded as delete- 
rious to the human frame. Even to touch it was supposed 
to occasion the loss of the hair ; while the sight of it would 
not fail to subdue the obstinacy of concealed pregnancy. 
The progress of science has exposed the errors, or perhaps 
tricks, of the earlier observers, and proved the innocence of 
an animal formerly invested with every repulsive and noxi- 
ous attribute. The A. depilans, the type of the genus, is 
of frequent occurrence on the British shores. The A. punc- 
tata of Cuvier may be regarded merely as a variety. 
Genus DotaseLLA.—Dorsal plate a solid shell. 
This genus differs from Aplysia, in the dorsal plate being 
calcareous and hard. The fore part of the body is narrow ; 
behind it is larger, and obliquely truncated. The disc thus 
formed-is circular, surrounded with a fringe of fleshy fila- 
ments. From the centre of this disc, a longitudinal slit ex- 
tends forward, a little way beyond the anterior margin, and 
