34*2 Dr Grant’s Observations on the Structure 
the apparent diameter of that orifice, from the great rarity of 
the air in the globule, compared with the dense medium of the 
water ; and when the globule escapes from the aperture to the 
surface of the water, the orifice appears to the eye to have en- 
larged its diameter considerably. I am inclined to think that 
some optical deception of this kind, a little assisted by the ima- 
gination, may have given rise to the belief of a systole and dia- 
stole of the fecal orifices. 
The opinion entertained by some naturalists, at an unknown 
period before Aristotle, that the sponge contracts itself when 
touched, has passed with little change, or examination, through 
a long lapse of ages, and is copied into the systems of Lamarck 
and Cuvier. From the remote origin of this opinion among the 
Greeks, it is not impossible that it may have been brought from 
Egypt by Herodotus, who has not given it a place in his writ- 
ings, but who appears to have studied Natural History with great 
minuteness while in that country. The vicinity of the priests and 
naturalists of Egypt to the numerous beautiful sponges which 
are known to abound in the Red Sea, that menagerie of zoo- 
phytes, would naturally tempt them to experiment on these ani- 
mals, and would give any statements they might make regard- 
ing their living phenomena, great authority among the natural- 
ists of Greece, and more distant countries. 
But it seems more probable, that it took its rise in Greece, 
where we find it first mentioned, and may have been occasioned 
by the following circumstance. The sponges along the boister- 
ous shores of the Hellespont, we are informed by Aristotle, were 
small, and of a hard texture, from the beating of the surge up- 
on them ; while they were much softer, and grew to greater mag- 
nificence, on the sheltered shores of the Peleponnesus. In the 
latter situation, their living properties could not fail to be fre- 
quently remarked by the naturalists of Argos, Sparta, Athens, 
and other large cities in that part of Greece, during their sur- 
veys of the maritime coasts ; particularly as the sponge was, at 
that time, extensively used by the Greeks for many economical 
purposes to which it is not now applied : as for lining the heavy 
casques of warriors, to diminish their friction, &c *. The great 
sponges along such calm and sultry bays, like the juicy aloe in 
Arist. Lib. v. cap. 16. 
