HISTORY OF ZOOPHYTOLOGY. 
29 
ing that they have no animal structure or individual organs, and 
exhibit no one function usually supposed to be characteristic of 
that kingdom. Like vegetables they are permanently fixed, — 
like vegetables they are non-irritable, — their movements, like 
those of vegetables, are extrinsical and involuntary,* — their nu- 
triment is elaborated in no appropriated digestive sac — and like 
cryptogamous vegetables or algae they usually grow and ramify 
in forms determined by local circumstances, and if they present 
some peculiarities in the mode of the imbibition of their food 
and in their secretions, yet even in these they evince a nearer 
affinity to plants than to any animal whatever. 
