SPONGES. 
27 
with the crimson and green specimens. You have never 
doubted that these are all sea-weeds, that is plants, alike. 
And yet if you saw these growing on their native rocks, 
plant-like as they are in form, you might discern, on careful 
examination with a pocket lens, that from various points 
of their surface tiny star-like circles of radiating points 
were protruding, that possessed spontaneous motions, and 
exhibited a shrinking sensitiveness to danger, and a power 
of seiziug and swallowing food ; and you would suspend, if 
not alter, your j udgment. 
If now, we ask, What is an animal 1 you will confess 
that the answer is not so easy as it appeared at first ; still 
there remain some characters common to all the beings 
that we have glanced at, and these we may perhaps con- 
clude to be inseparable from, and distinctive of, animal 
existence. Of these characters, the most constant and the 
best defined are the power of spontaneous motion, and the 
possession of a stomach, or at least an enclosed cavity, in 
which other substances are converted into nutriment. 
With regard to the former of these characters, what 
shall we say to the Sensitive plants of the tx - opics, the 
pinnate leaflets of which fold together, and the jointed 
leaf-ribs fall, on the rude touch of a foreign body 1 What 
to the plant called Venus’ Fly-trap (Dionaa muscipula), 
found in the marshes of North America, whose broad 
two-lobod leaves, armed with strong teeth standing up 
from the surface, ordinarily lie widely expanded ; but 
when an insect touches their hairy centres, instantly fly up 
like a rat-gin, the teeth cross each other, and the offend- 
ing fly is pierced, and held a prisoner until it dies 1 What 
to the Gorachand of Bengal (Jledysarum gyrans), whose 
