ORDER III. CORALLIFERI. — SPONGES. 359 
are phosphorescent; when stimulated or touched in one place, the light 
spreads upwards from one branchlet and one polypus to another, until it 
reaches the summit, while all the parts below remain dark. When the 
whole is thrown into a vase filled with fresh water, it emits .sparks on all 
sides, affording a most beautiful spectacle. 
Sponeta.— The Sponges. These are well-known fibrous, marine bodies, 
whose only sentient portion, according to Cuvier, is a sort of thin eclatine, 
which soon dries off. The Sponges, of which we see in our museums but 
the naked skeleton, are endowed with a wonderful variety of shape and tint. 
Like the polypi and corals, they imitate every form of vegetation, and 
decorate the submarine grounds of the warmer seas with their fantastic 
shrubberies. 
On examining a sponge, its centre will be found pierced with wide pas- 
sages or channels, which, branching out like trees, terminate in the innumer- 
able small oscula or pores with which its surface is covered. Dr. Grant has 
made the highly interesting discovery, that the latter continually imbibe 
water, which is expelled by the former as long as the sponge retains life. In 
this manner a perpetual circulation is maintained, providing the sponge with 
nourishing particles and oxygen, and performing the functions both of an 
alimentary tube and a respiratory apparatus. Thus even in the lowest 
stages of existence the bounty and admirable foresight of Nature appear in 
all their plenitude. 
The propagation of the sponges is provided for in a no less wonderful 
manner. Their young eges, or sporules, germinate on the sides of the 
canals, forming innumerable minute bud-like points. These, as they in- 
crease in size, are gradually clothed with vibratile hairs, or cilia, and finally 
detaching themselves, move about freely in the water, the united action of 
the perpetually vibrating cilia creating strong currents round their little 
bodies, and driving them forwards. In the open sea their wanderings con- 
tinue for a short time, until, if they be not devoured on the way, they reach 
a place suitable for their further development, where they attach themselves 
forever, bidding adieu to all youthful rambles, and only desirous henceforth 
of leading the quiet sedentary life of their parents. 
S. Communi’s. —The Common Sponge, so serviceable in our households, 
is most abundant in the Lycian Seas, the most valuable kinds of which 
abound “about the Gulf of Macri, along the Carian coast, and round the 
opposite islands. The species which live immediately along the shore near 
the water’s edge, though often large, are worthless. These are of many 
colors ; some, of the brightest scarlet or clear yellow, form a crust over the 
faces of submarine rocks; others are large and tubular, resembling Holo- 
thurize in form, and of a gamboge color, which soon turns to dirty brown 
