Cuvierian System of Zoology, 309 



M. Franz Unger ascertained, also, that the period of animal 

 existence enjoyed by these globules (or monades, as he calls 

 them) is about one hour. The first sign of this portion of their 

 life having ceased is, a change from the oval to the globular 

 form, and an equal diffusion of the green colouring matter. 

 In about six hours, the globule has become nmch more trans- 

 parent, and puts forth an appendage, and on the third day a 

 second one, by which the young plant becomes fixed to the 

 side of the glass vase, or- any other body in contact with it. 

 About the eleventh day the fructification of the new plant is 

 apparent at the summit of the principal branch. A 



Art. II. The Cuvierian^ or Natural^ System of Zoology, 

 Essay 2. On the Living Principle and its Effects ,' on Organisation 

 and Muscular Motion ; and on Sensation, and the Intellectual 

 Faculties and Instincts of Animals, By B. 



In the preceding essay I selected, from the introduction 

 to Cuvier's Regne Animal^ his descriptions of those parts of 

 the animal physiology that were necessary to explain the prin- 

 ciples on which his four grand divisions of animals, the verte- 

 brated,- the molluscous, the articulated, and the radiated, are 

 founded. There are other parts of physiology, which, with 

 what has been already given, may be regarded as form- 

 ing the very rudiments of the natural historj^ of organised 

 sentient beings. These are, for the most part, concisely and 

 luminously described by our author; and I think it desirable 

 to state them to the English reader, before we proceed to his 

 farther description and subdivisions of vertebrated animals. 



Without some acquaintance with the leading facts in phy- 

 siology, we can have no scientific knowledge of zoology, or 

 of the principles on which a natural system of classification 

 should be founded. As well might we expect to learn the 

 mechanism of different timepieces, by a mere inspection of 

 the dial-plates and the cases in which they are enclosed, as to 

 gain a scientific knowledge of living beings, by only looking 

 at their external forms. The principles of a new science, 

 however clearly they may be stated, are never thoroughly 

 understood until a practical application of them has been 

 made. We then turn to them again, and perceive their full 

 force and meaning. This is even the case with the axioms in 

 geometry. I think it necessary to premise these remarks, 

 lest any of our readers should deem this part of the subject 

 less inviting than what is to succeed. 



Y 3 



