ZOOLOGY. 7 



more than it follows that their want of muscular fibre justifies us 

 in denying to them voluntary motion, which the unprejudiced 

 observer may recognise even in the most simple animals. 



As to chemical composition Nitrogen, it is true, is not ex- 

 clusively an animal principle: but still it occurs as an ultimate 

 constituent of animal organisation in much greater quantity than 

 in plants. In plants, on the other hand, Carbon is predominant. 



Not long ago, it was believed that a transition from Plant-Life 

 to Animal-Life had been observed 1 . L. C. TREVIRANUS had 

 remarked that the spores of Confervas move like Infusories 2 . A 

 few years since UNGER described this phenomenon in Vaucheria 

 clavata, and thought that he had surprised plants at the very 

 moment of their becoming animals 3 . These sporidia move by 

 means of cilia, but cannot on that account be considered animals 4 . 

 Kather ought we, from such instances, to conclude that cilia are no 

 exclusive character of the animal kingdom. The same may be said 

 of a similar motion which GRANT observed in sponges, which, as 

 little, on that account, are animals. 



As we have already remarked above, the difference between 

 plants and animals will always be more apparent as the organisa- 

 tion becomes more perfect and more complicated: the difficulty 

 occurs in the case of the most simple vegetable and animal forms ; 

 and here may be applied what Ovid says of the change of colour in 

 the rainbow, 



Usque adeo quod tangit idem est, tamen ultima distant. 



Met. vi. 67. 



Zoology. 



There are three parts of Natural History, as there are three 

 great divisions of the bodies which occur on our Earth. We sepa- 

 rate Natural History into Mineralogy, Botany and Zoology, as we 



1 See the earlier observations on this point in G. B. TfiEViRANUS* Biologic, oder 

 Pliilosophie der lebenden Natur. 8vo. II. p. 344. 



2 Beitrage zur Pflanzenphysiologie. Gottingen, 1811. 8vo. pp. 78, 79. 



3 Die Pflanze im Momente der Thierwerdung. Wien. 1843. 8vo. 



4 C. DE SIEBOLD, Dm. de finibus inter regnum animale et vegetabUe conslituendis. 

 Erlangse, 1844. 4*0. 



