100 ZOOPHYTES. 
mode of developement,—the character of their food, it consisting of 
organized and not unorganized matter—the peculiarities of the pro- 
cess of digestion and the ejection of excrementitious matter—the 
influence exerted on the atmosphere by the aeration of the circu- 
lating fluid—as well as their voluntary motions, remove zoophytes far 
from the vegetable kingdom. The fact of an imperfect nervous sys- 
tem, explains the apparent resemblances. The simplicity of their 
internal organization is due to this ; and it also accounts for the great 
number of possible organic centres in a polyp, each exerting an 
influence around only to a very limited extent, capable of budding 
out a young animal, either while connected with other parts of a 
polyp, or when separated as an artificial section. It is even probable 
that the radiate form, characteristic of the lower orders of animals, 
and also of a great part of the vegetable kingdom, is due to the simple 
laws of organic developement, which, in these cases, are either un- 
controlled by other directing forces that act through the developing 
nervous system, or are so controlled only to a very limited degree.* 
* See farther, the note to § 108. 
