NATURAL HISTORY. 69 
instantaneous expansion, and is never com- 
pletely closed, for its prey, which it always 
swallows alive, may be observed moving about 
in the first cavity, and endeavouring to make 
its escape through the contracted opening. All 
the digestive cavities or stomachs are preserved 
in their proper situation by a transparent mus- 
cular annulus between each of them. These 
diaphragms possess considerable contractile 
power, and are attached by their outer circum- 
ference to the muscular stratum, under the skin 
of the animal, while their inner margin surrounds 
the contracted parts of the alimentary canal, 
and is fastened to it. The fibres of these mus- 
cular plates diverge like rays, analagous to those 
in the iris of the human eye, and vary the 
aperture of the stomach, like the pupil of the 
eye, in the latter case. At 0 is situated a pul- 
satory organ, which terminates in two nervous 
lobes; these are scarcely discernible in the 
young specimens, and are not represented in 
the drawing. 
The digestive power of the stomachs must be 
very considerable, as the food which they prefer 
is crustaceous. They will often devour mono- 
culi greater in diameter than their own bodies, 
and that with a degree of rapidity and insatia- 
