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?. L. C. Treviranus had 
remarked that the spores of Conferve move like Infusories*. A 
few years since UNGER described this phenomenon in Vaucherta 
clavata, and thought that he had surprised plants at the very 
moment of their becoming animals*. These sportdia move by 
means of cilia, but cannot on that account be considered animals‘. 
Rather 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.— 
Me. 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. R, TREVIRANUS’ Biologie, oder 
Philosophie der lebenden Natur. 8vo. Il. p. 344. 
2 Beitriige zur Pflanzenphysiologie. Gottingen, 1811. Svo. pp. 78, 79. 
3 Die Pflanze im Momente der Thierwerdung. Wien. 1843. 8vo. 
4 ©. pe Steno, Diss. de finibus inter regnum animale et vegelabile constituendis. 
Erlangee, 1844. 4to. 
