1/2 ROMANCE OF LaW LIFE AMONGST PLANTS. 



and not plants. The strongest evidence in support 

 of this theory was undoubtedly the peculiar spon- 

 taneous movements of which they were capable, such 

 movements, it was contended by Ehrenberg, being 

 produced by the protrusion of cilia or feet from the 

 extremities of the frustule. Subsequent observers 

 failed to detect these organs of locomotion. Un- 

 doubtedly the old definition of the attributes of 

 plants and animals had something to do with 

 creating a prejudice in favour of the animal nature 

 of diatoms ; this definition summarily disposed of 

 the question by pronouncing that animals were 

 organisms endowed with locomotion, and plants were 

 organisms without locomotion. Afterwards, when it 

 came to be demonstrated that some animals, like 

 sponges, had no locomotion, and many plants, espe- 

 cially algae, were locomotive, it became much easier 

 to believe that the mere fact of locomotion did not 

 prove animality. Under these changed conditions 

 the nature of the motion in the disputed organisms 

 came under discussion, it being contended that the 

 movements were entirely different from those which 

 characterized other locomotive plants, were con- 

 ducted by instinct or intelligence, and consequently 

 were of an animal nature. "If nature," writes 

 Humboldt, "had endowed us with microscopic 

 powers of sight, and if the integuments of plants 

 were transparent, the vegetable kingdom would by 

 no means present that aspect of immobility and 

 repose under which it appears to our senses." After 

 it came to be doubted whether any organs of locomo- 

 tion existed, such as Ehrenberg described, we find 



