545 
and Functions of the Sponge. 
feet produced by the soft gelatinous matter which occupies the 
interstices of the horny fibres, while Lamarck and Cuvier seem 
to consider it as a property belonging to the entire mass of the 
animal. Lamarck, in his valuable memoir on this animal, and 
in his recent great work, has even entered into an explanation of 
the cause of this trembling motion or sudden contraction of its 
body when touched, by comparing it, as Ellis had done before 
him, with the Alcyonium ; and he conceives, that the existence 
of this property in the sponge is indisputable, both from its ana- 
logy with these compound animals, and from the testimony of 
the Greeks. So great is the analogy, he conceives, between the 
sponge and the different species of Alcyonium, which present 
superficial polypi, projecting from a fleshy contractile base, that, 
if the sponge were examined under water with the necessary pre- 
cautions, the polypi might be seen projecting from the gelatinous 
matter on its surface, and have hitherto escaped observation, on- 
ly from their smallness and colourless transparency. 
It is important to inquire, whether the mass of the sponge 
possesses any contractile power in the living state, because, in 
the absence of all positive evidence of the existence of polypi, 
this property of irritability constitutes its sole claim to be re- 
garded as an animal in the zoological system of Lamarck, which 
is now adopted by most of the naturalists of Europe. As the 
division of matter into the mineral, vegetable, and animal king- 
doms, is entirely founded on assumed characters and arbitrary 
definitions, Lamarck has assumed irritability as the sole discri- 
minating test of animal life, and has shown, that this singular 
property of reaction becomes less and less apparent as we ap- 
proach the lower limit of the animal kingdom : And conse- 
quently, if the sponge cannot be made to manifest any sign of 
irritability, it must, upon his principles, be excluded from the 
animal kingdom, and must be regarded as a vegetable, from its 
other properties of growth and generation. The discovery of 
irritability in the mass of the sponge, would not only determine 
its true animal nature, but would likewise confirm the analogy, 
which has long been supposed to exist, between it and the alcy- 
onium, and thus point out its true place in the scale of animals. 
This contractile power, if ascertained, would afford an easy and 
satisfactory explanation of the mysterious currents from the 
