250 ILYANTHID^E. 



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 column. 



The stomach is sometimes protruded, and inflated so as 



