216 ON THE CLASSES OF THE 



like plants, to the absorption of their external pores. They 

 must be esteemed animals, on account of their peculiar 

 irritability, but are vegetables in almost every other respect. 

 Of such an ambiguous nature indeed are these simply con- 

 structed and minute atoms that they confound every no- 

 tion, even the most clear, which we may have endea- 

 voured to form of animal life ; atoms that, were their 

 importance to be estimated according to their size, would 

 be utterly neglected in the study of nature, but which 

 nevertheless, because organized matter in them is reduced 

 to the most simple form of cellular tissue, and life, as it 

 were, is at its very lowest ebb, have employed the time and 

 labours of Hooke, Leuwenhoeck, Spallanzani, Muller, and 

 Lamarck. And this method of investigation is surely more 

 philosophical than that of those who attempt to form ac- 

 curate ideas of animal life by studying it only in its most 

 complex shape, which is just as if we could hope to pe- 

 netrate into the depths of the Newtonian philosophy with- 

 out being previously acquainted with the simpler ele- 

 ments of mathematical science. 



ACRITA. 



The genus Monas may be taken as the type of the In- 

 fusoria, since it consists of the smallest and least compli- 

 cated of all known animals. From these, by means of be- 

 ings still only visible by the assistance of a microscope, but 

 gradually obtaining some sort of appendages so as to give 

 them the definite form of which the Monades are destitute, 

 we proceed to the Polypi rudes, which may perhaps 

 be hereafter found to be a circular group, composed as 

 well of Cuvier's Infusoires rotiferes as of his Polypes nus. 

 The Polypi rudes according to this idea, for which 



