166 ANIMALS AND PLANTS vi 



known to be some of the most widely-prevalent 

 phenomena of vegetable life. 



Agardh, and other of the botanists of Cuvier's 

 generation, who occupied themselves with the 

 lower plants, had observed that, under particular 

 circumstances, the contents of the cells of certain 

 water-weeds were set free, and moved about with 

 considerable velocity, and with all the appearances 

 of spontaneity, as locomotive bodies, which, from 

 their similarity to animals of simple organisation, 

 were called " zoospores." Even as late as 1845, 

 however, a botanist of Schleiden's eminence dealt 

 very sceptically with these statements; and his 

 scepticism was the more justified, since Ehren- 

 berg, in his elaborate and comprehensive work on 

 the Infusoria, had declared the greater number of 

 what are now recognised as locomotive plants to 

 be animals. 



At the present day, innumerable plants and free 

 plant cells are known to pass the whole or part of 

 their lives in an actively locomotive condition, in 

 no wise distinguishable from that of one of the 

 simpler animals ; and, while in this condition, their 

 movements are, to all appearance, as spontaneous 

 as much the product of volition as those of 

 such animals. 



Hence the teleological argument for Cuvier's 

 first diagnostic character the presence in animals 

 of an alimentary cavity, or internal pocket, in 

 which they can carry about their nutriment has 



