350 ANIMAL NATURE OF UIATOME.E. 



same being, he says, may pass from the animal to the 

 vegetable nature, or from the latter to the former, and 

 again return to its original state. This opinion is not 

 new, for it was previously held by Agardh, by Gaillon, 

 and by Bory St. Vincent ; but the facts which lead 

 Kiitzing to adopt it are so precise and so well described, 

 that they do not admit the easy charge of incorrect 

 observation, by which many have hitherto been satisfied 

 to answer arguments deduced from similar facts. He 

 sees microscopic beings corresponding exactly with the 

 descriptions and figures given by Ehrenberg, furnished 

 with organic peculiarities, and presenting vital phenomena 

 generally regarded by Ehrenberg and others as characters 

 of animal life, assume in their successive and natural 

 development, form, organisation, and life, such as are 

 generally attributed to plants. And from these plants 

 he sees reproductive bodies generated, similar to the 

 seeds of superior and spores of inferior plants, equally 

 endowed with characters of animality, becoming, however, 

 subordinated to those of vegetable life. The fact is true, 

 and may be easily verified by any one in the habit of 

 making microscopic observations. And the explanation of 

 this fact appears to me equally easy. If there are beings 

 which, when they attain their perfect development, prove 

 themselves to be decidedly vegetable, although during 

 the first portion of their existence they presented some 

 phenomena of animal nature, this proves that those phe- 

 nomena do not exclusively belong to animals, and that 

 we cannot draw from them absolute characters of animal 

 nature. The imperfection, which we have already shown 

 to be inherent in every notion we can form of the animal 

 or vegetable kingdom, begins to diminish after such 

 considerations, and it is under this point of view that we 

 purpose to undertake the examination of Diatomeae, 

 carefully separating in the characters they present, 

 those which they hold in common with vegetables from 

 those in common with animals, and inquiring if they do 

 not possess some exclusively with one or the other which 



