Actions of Volcanoes. 285 
and carry on the operation of extending their habitations. In 
these operations, however independently each seems to act in 
the production of its own cell, or in the extension of its own 
immediate neighbourhocd, the whole are regulated by some 
common mysterious principle, by which they all concur towards 
the production of a structure that would rather seem to have 
been directed by one mind. Now nothing very analogous to 
this takes place in the animal creation, except in the case of the 
gregarious insects, that construct a common habitation for 
breeding, such as the bees and the ants. In these there is a 
possibility of personal communication ; and that there is such, 
is proved by the accurate researches of many naturalists. No 
such communication can take place among the coral animals, 
because each is fixed and rooted to its cell, of which it forms a 
part. It may be considered, indeed, that the whole of the 
colony are parts of the structure which they inhabit, just as 
flowers are of a plant. 
This analogy is very strongly confirmed by attending to the 
genus vorticella, a soft animal, incapable of constructing such 
a habitation as the coral, yet possessing some very striking 
analogies to it. The simple vorticella is independent, and 
swims at liberty; not unaptly resembling, at the same time, a 
flower, or a bud just expanded ; appearing to consist of a body 
resembling a calyx, provided with tentacula, that have been 
compared to stamina or petals. But if we proceed from the 
simplest vorticella onwards, we find a species which is im- 
moveably fixed, by a pedicle of animal fibre, to the spot where 
it was produced, or is at least only capable of floating 
through the water within narrow limits. In further progress, 
two are united by one stem, and at length there are found one 
or more species, in which a single stem produces numerous 
ramifications, each of which is terminated by the calyx-shaped 
animal, or flower, if we may so call it. In this case, each 
animal is partially independent, yet all depend on the whole ; 
so that were it not for the demonstration of its being of an 
animal nature, it might be esteemed a vegetable. In what way 
this mutual dependence and co-operation of many animals, to 
