250 
ILYANTHID^. 
they prove to be granular nuclei in the substance of the 
skin, dense in the centre, and gradually thinning to an 
undefined circumference, elevating the surface with a smooth 
rounded outline to a height about equal to their diameter ; 
viz. about .002 inch. Many of them certainly have a 
shallow pit on the summit, and I am persuaded that their 
adhesion is a sucking. In the middle part of the body, 
these warts are elongated transversely, and have a ten- 
dency to run in close-set annular lines. 
I have not been able to satisfy myself of the character 
of the inferior extremity. It often appears as if it were 
distinctly perforate; but I believe this is an illusion, 
produced by the following phenomenon. As the animal 
lies on its side, it is continually being constringed, the 
constriction gradually moving downward till it passes off 
at the extremity. The parts above and below being in- 
flated, and being as transparent as glass, one sees, looking 
directly at the extremity, the inner edge of the constriction, 
through the transparent integument, exactly like a ter- 
minal orifice, at the moment before it passes off. 
The manners of the species are lively and pleasing: it is 
very susceptible of alarm, when it closes and disappears in 
its burrow with great quickness ; it is, however, soon full- 
blown again. Under irritation, as when fine clay is mixed^ 
with the water, the tips of the tentacles are jerked from 
side to side with a suddenness and force that contrast 
with the languor common to the tribe, and which seem to 
indicate both a higher nervous sensibility, and also a 
greater development of the muscular system. 
My experience, as well as that of Mr. Peach, shows that 
it is a species well adapted for an aquarium, and that no 
special treatment is needful beyond a layer of sand equal 
in depth to the length of the cohimn. 
Tlie stomach is sometimes protruded, and inflated so as 
