ZOOPHYTES. 143 



branches of the mechanical functions are an- 

 swered by the organization both of the vegetable 

 and the animal systems : but those of the latter 

 belong exclusively to the functions of animal 

 life. The power of locomotion, more especially, 

 constitutes the most general and palpable fea- 

 ture of distinction between these two classes of 

 beings. A plant, during the whole period of its 

 existence, is fixed to the spot m here it was first 

 produced, and is dependent for the continuance 

 of its life on local circumstances ; such as the 

 nature of the soil in which its roots are embed- 

 ded, and the qualities of the air and w^ater in its 

 immediate vicinity. It is exposed to the action 

 of the surrounding elements, and afi*ected by 

 their vicissitudes, without the means of retreat, 

 and without the power of reaction. With respect 

 to all external agents, indeed, vegetables may 

 be regarded as passive beings. Very different 

 are the condition and destination of animals. 

 Excepting a few^ among the lower orders of the 

 creation, such as Zoophytes and Mollusca, all 

 animals are gifted with the power of sponta- 

 neously changing their situation, according to 

 their several wants and necessities, and are thus 

 enabled to seek and to choose those objects 

 which are salutary, and to avoid or reject those 

 w^hich are injurious. Nature has, for these 

 purposes, furnished them with a more complex 



