ON ZOOPHYTES. 525 
As for the asteriz or sea-stars, which in one passage he 
enumerates among the equivocal beings between the animal 
and plant, while in another he ranges them with the testacea, 
the little that he says is very incomplete, and not very easily 
to be understood. 
The medusz also appear to have been known to Aristotle, 
but he confounded them with the actiniz, properly so called, 
under the common denomination of sea-nettles, acalephe and 
knide, which signify nettle. These, again, are beings whose 
nature is equivocal between the plant and the animal. In 
fact, he tells us, it is the property of an animal to move itself, 
to direct itself towards its food, to feel what it encounters, and 
to use in its defence the firm and hard parts of its body. But 
to have an organization extremely simple, to attach itself with 
facility to rocks, and to have a mouth, but no apparent orifice 
for the issue of the excrements; all this is more of the nature 
of the plant. In other places of his works, Aristotle enters 
into some details of organization and manners, respecting his 
acalephai. Among other matters, he tells us that there are 
some which remain fixed upon rocks, and other submerged 
bodies, and others which are detached from them ; an obser- 
vation which has led several authors to think that he was 
speaking of actiniz and medusz; but this opinion is not free 
from doubt. 
Of all the rest of the animals which constitute the zoophytes 
of modern zoologists, it does not appear that Aristotle was 
acquainted with any except the sponges, respecting which he 
gives us some details of tolerable extent. 
As to the animals which he calls polyp?, it is well known, 
that they are not the same as those so called in the present 
day. We have already seen in our observations on the mol- 
lusca, that they are the octopi, respecting which he has left 
us some valuable remarks. 
