650 
PROTOZOA. 
spongy incrustation ; whilst others shoot up a branched stem into the water ; and others again 
hang freely from the sea-weeds floating in the ocean. Many sponges are remarkable for 
the singularity of their forms, sometimes spreading into broad leaves or fans; sometimes 
they are cylindrical like a thick stick ; 
now assuming the form of a hand, and often 
hollowed out in the shape of a cup, with a 
foot like a vase. They occur abundantly on 
all shores from Greenland to Australia, but 
are most numerous and gigantic in hot lati- 
tudes. The common sponge of commerce 
is chiefly found in the Mediterranean, where, 
especially among the beautiful Isles of Greece, 
an important fishery and traffic are carried 
on for this article. " At the Cyclades, for 
instance, sponge-diving forms the chief em- 
ployment of the population. The sea is at 
all times exceedingly clear, and the experi- 
enced divers are able to distinguish from 
the surface the points to which the Sponge 
is attached below, when an unpractised eye 
could but dimly discover the bottom. Each 
boat is furnished with a large stone attached 
to a rope, and this the diver seizes in his hand 
on plunging head foremost from the stern. He 
does this in order to increase the velocity of 
descent, thus economizing his stock of breath ; as well as to facilitate his ascent when exhausted 
at the bottom, being then quickly hauled up by his companions. Few men can remain longer 
than two minutes below ; and as the process of detaching the sponge is tedious, three and some- 
times four divers descend successively to secure a particularly fine specimen." This fishery 
appears to have been prosecuted in the same locality in very ancient times. Tournefort states 
that of so much importance is it considered in the region where it is carried on, that no youth is 
allowed to marry until he has given proof of his proficiency in the art of diving. 
THE COMMON SPONGE. 
Class III. KMIZOFOHA- 
In the deposit formed at the bottom of fresh-water ponds, we may often meet with a singular 
minute gelatinous body, which constantly changes its form even under our eyes, and moves 
about m its native element by means of finger-like processes, which it appears to have the 
power of shooting out from any part of its substance. This shapeless gelatinous mass is an 
animal, the Amoeba diffluenSy well known to microscopic observers under the name of the Proteus, 
from the continual changes of shape which it presents to our notice, (See engraving, p. 646.) It 
consists entirely of the granular gelatinous matter already mentioned as sarcode, and appears to be 
nearly homogeneous in its texture ; that is to say, the outer surface exhibits no signs of being 
bounded by any distinct membrane or layer of a firmer consistence than the rest of the body. 
No indications of any internal organization are to be recognized in this creature ; for it pos- 
sesses neither mouth nor intestinal canal. It is not to be supposed, however, that the animal 
keeps a perpetual fast, or that its food is entirely of a fluid nature. On the contrary, it appears 
to be, in its small way, of an exceedingly voracious disposition, seizing upon any minute aquatic 
animals or plants that may come in its path, and appropriating them to the nutrition of its own 
gelatinous person. 
