16 
INTRODUCTION. 
IY. 
movement. But the sponges can scarcely be far removed from Fungia, nor can 
that be separated from other corals : so that, though I am aware some naturalists 
of eminence regard the sponges as vegetables, I cannot subscribe to that opinion, 
but rather view them as exhibiting to us animal organization in its lowest con- 
ceivable type, and parallel to vegetable organization, as that exists in the lowest 
members of the class of Algae. 
This hasty glance at the animal kingdom teaches us that voluntary motion is a 
character variable in degree, and at length reduced almost to zero within the 
animal circle. On the other hand, we know that movements of a very extra- 
ordinary character exist among the higher vegetables. Not merely the movement 
of the fluids of plants within their cells, which has at least some analogy with the 
motion of animal fluids ; but in such plants as the Sensitive-plant, the Venus’s 
Flytrap ( Dioncea) , and many others, movements of the limbs (shall I call them ?) as 
singular as those of the Algae-spores, are sufficiently well known. And these move- 
ments are affected by narcotics in a manner strikingly similar to the operation 
of similar agents on the nervous system of animals. The common sensitive-plant, 
indeed, only shrinks from the touch, but in the Desmodiiim gyrans a movement of 
the leaves on their petioles is habitually kept up, as if the plant were fanning itself 
continually. Such vegetable movements as these strike us by their rapidity, but 
others of a like nature only escape us by their slowness. Thus the opening of the 
leaves of many plants in sunlight and their closing regularly in the evening in 
sleep ; the constant turning of the growing points towards the strongest light, and 
other changes in position of various organs, are all vegetable movements which 
would appear as voluntary as those of the Algae spores if they were equally rapid. 
Their extreme slowness alone conceals their true nature. 
So then we find animals in which motion is reduced almost to a nullity ; and 
vegetables as high in the scale as the Leguminosce exhibiting well marked move- 
ments, facts which sufficiently establish the truth of our position that mere motion is 
no proof of animality. But subtracting their movements from the Algae-spores, 
what other proof remains of their being animalcules ? None whatever. They do 
not resemble animalcules either in their internal structure, their chemical compo- 
sition, or their manner of feeding ; and their vegetable nature is sufficiently 
marked by their decomposing carbonic acid, giving out oxygen in sunlight, and 
containing starch. 
In the Vaucheria clavata , one of the species in which spores moved by cilia were 
first observed, the spore is formed at the apices of the branches. The frond in 
this plant is a cylindrical, branching cell, filled with a dense, green endochrome. A 
portion of the contained endochrome immediately at the tips separates from that 
which fills the remainder of the branch ; a dissepiment is formed, and that portion 
cut off from the rest gradually consolidates into a spore, while the membranous 
tube enlarges to admit of its growth. The young spore soon becomes elliptical, 
and at length, being clothed with a skin and ready for emission, it escapes through 
an opening then formed at the summit of the branch. The wdiole surface of the 
spore, wdien emitted, is seen to be clothed with vibratile cilia whose vibrations 
propel it through the water until it reaches a place suitable for germination. 
