VIL] ANIMALS AND PLANTS. 153 



since Ehrenberg, in his elaborate and comprehensive 

 work on the Infusoria, had declared the greater num- 

 ber 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 move- 

 ments 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 broken down, 

 so far, at least, as his mode of stating it goes. And, 

 with the advance of microscopic anatomy, the univer- 

 sality of the fact itself among animals has ceased to 

 be predicable. Many animals of even complex struc- 

 ture, which live parasitically within others, are wholly 

 devoid of an alimentary cavity. Their food is pro- 

 vided for them, not only ready cooked, but ready 

 digested, and the alimentary canal, become super- 

 fluous, has disappeared. Again, the males of most 

 Eotifers have no digestive apparatus; as a German 

 naturalist has remarked, they devote themselves en- 

 tirely to the " Minnedienst," and are to be reckoned 

 among the few realisations of the Byronic ideal of a 

 lover. Finally, amidst the lowest forms of animal life, 

 the speck of gelatinous protoplasm, which constitutes 



