28 PHILOSOPHY OF ZOOLOGY. 



According to this view, the germs of the ferns and palms 

 first expanded their leaves, and afterwards those of the sta- 

 niiniferous vegetables. With regard to animals, it may be 

 supposed that the germs of the zoophytes only, were first 

 disclosed ; afterwards those of the testaceous mollusca ; and, 

 finally, those of the vertebral animals : That the organized 

 beings of the first periods flourished during the continuance 

 of the circumstances which were suitable to their growth ; 

 and that the change which prepared the way for the evolu- 

 tion of those which lived at a subsequent period, contributed 

 to the extinction of the earlier races. 



According to this statement, there is little difficulty in 

 accounting for the extinction and revival of the different 

 races of the less perfect animals and vegetables, whose 

 germs appear, even at present, to be regulated according 

 to such circumstances. But it offers no solution of the 

 difficulty attending the preservation of the germs of the 

 more perfect animals, many of which are inseparably con- 

 nected with the parent, and require the continuance of her 

 life to preserve vitality until the period of evolution. If, 

 then, the present races of quadrupeds did not exist at the 

 time when the mammoth and the other extinct quadrupeds, 

 whose bones CUVIER has described with so much accuracy, 

 were the denizens of our plains, at what period, and under 

 what peculiar physical circumstances, were they called into 

 being? Is the generation of organized beings simultaneous 

 or successive ? Have they all been created at once ; but, 

 in the progress of time, so modified by the influence of ex- 

 ternal agents, as now to appear under different forms? 

 Or have they been called into being at different periods, 

 according as the state of the earth became suitable for their 

 reception *. The latter supposition is countenanced by 

 many geological documents. 



* See CUVIER' s " Recherche* sur ics Osr--mens Fossiles dc Quadrupedes,*' 

 J8I2. 2 



