506 ANIMAL NATURE OF UIATOMK^E. 



wall, seems confirmed by the valuable observations of 

 Kiitzing, already referred to, respecting the mobility of 

 the inferior Algae, of sporidia, of spores, and spirilla. But 

 even if we admit this idea, we can deduce no other than 

 the following principle from the facts hitherto known. 

 The primordial vegetable cells (internal or naked pri- 

 mordial utricle), have, hke animal cells, the wall con- 

 stituted of a quaternary azotised substance, and possess 

 a mobility similar to animal mobility. Yet there remain 

 material differences in the contents. But, if this were 

 not so, if observation failed to detect a material difference 

 between the rudiments (jormor^/w) of the two kingdoms, 

 no one, from that circumstance, would have a right to 

 maintain that the difference does not exist. When we 

 compare together the rudiments of plants, or those of 

 animals, do we find material differences corresponding to 

 the almost infinite varieties of form and organisation which 

 ensue with successive development ? It is necessary to 

 repeat, that our senses are limited, and that if we desire 

 to pass beyond those boundaries by powers of reasoning, 

 we may do this by no other means than reliance upon 

 other facts exactly observed. Taking advantage of in- 

 stances in which the power of our senses is improved, we 

 reason upon others where that power is more limited. 

 Thus, in respect to the rudiments of organic beings, the 

 observation of their successive development proves that 

 even when those rudiments do not manifest material 

 differences to our senses, these still exist. 



Still we ought, in every way, to be extremely cautious 

 in deducing anything from these observations which may 

 seem to prove the animal nature of vegetable germs, even 

 when they are made with great accuracy; inasmuch as 

 we can controvert them by others equally exact of a con- 

 tradictory nature. Such are those made by Nageli upon 

 his Conferva glomerata, var. marina, and upon the Achlya 

 prolifera. In the former, especially, he could trace the 

 eutophytic development of the Bodo viridis, which, at a 

 certain period, almost exactly resembles sporidia, but 



