GLAUCUS. 115 
closely watching the devouring process, which was 
effected by an apparently sucking motion; and at 
this time all the digitated processes of the fins 
were floating about, as at other times, when the 
animal was atrest. But I did not observe, in one 
single instance, that they were of any use to the 
animals, either to aid in the capture, or to securely 
hold their prey when in the act of being devoured ; 
for the animal seems to depend merely upon the 
mouth in capturing its prey, as, in this and other 
instances which I had opportunities of observing, 
they seized their prey instantly with the mouth, 
and held it by that power alone, whilst by a kind 
of sucking motion the prey was devoured. The 
digitations may, therefore, only be regarded as 
appendages to the fins, to aid the animal, perhaps, 
in the direction of its movements, as it was observed 
that they turned and twisted them about during 
the progressive motion—that is, when this tardy 
animal is pleased to progress,—as if in some way 
or other to direct the movements of the animal. 
“The Glaucus, after eating the tentacles, and 
nearly the whole of the soft under surface of its 
prey, left the horny portion, and remained tranquilly 
reposing upon the surface of the water after its 
meal, the only motion visible in the animal being 
the playing of the digits of its fins. The mutilated 
remains of the Porpita sank to the bottom of the 
glass. 
“Soon after, another Glaucus began a devouring 
attack upon another Porpita which had been placed 
in the glass, eating a little of it, and then ceasing 
after a short meal, occasionally renewing the 
attack at short intervals. On examining the Porpita 
which had been partially devoured by the ravenous 
