G. SPONGIA. 
151 
metre; and their diameter from the thickness of a 
thread to many decimetres. 
We have chosen the forms of the Spongia to cha- 
racterise the sections, beginning with those of shape- 
less masses, then taking the more regular cup or cra- 
ter form, which in succeeding species becomes lobed, 
gradually assuming the form of branches, till the plant 
or tree-like sponge appears. 
But these singular and useful beings, to which we 
are indebted for the sponge, still continue to be un- 
known; no research has hitherto discovered more 
than a gelatinous substance, resembling the white of 
an egg, which surrounds the sponge when undisturbed 
on its native site, but so fugitive that it runs imme- 
diately away when taken from its natural element. 
The Spongias are very common between the tropics, 
less so in the temperate regions, and wholly disappear 
in the neighbourhood of the Polar circles. 
I shall not in these limited descriptions detail the 
manner of procuring the sponge, but content myself 
with reciting two circumstances that prove the esti- 
mation in which it is held in the countries where it is 
procured. 
In the island of Nicaria, one of the Grecian Archi- 
pelago, the young men are not allowed to marry 
until they have given proofs of their skill in diving 
for the sponge : Hasselquist also mentions a small 
island named Himia, near Rhodes, where the young 
women cannot marry until they have dived an ap- 
pointed depth, and procured a certain quantity of 
sponge. 
