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. 



