METAMORPHOSES OF ANIMALS. 153 



apophyses of their vertebrae, whilst the vertebrae themselves 

 are wanting. It would be the same, were the Sturgeons of 

 one of the American rivers to become petrified. As the 

 apophyses are the only bony portions of the vertebral 

 column, they alone would be preserved. Indeed, fossil 

 Sturgeons are known, which are in precisely this condition. 

 395. From the fact above stated, we may conclude 

 that the oldest fishes have not passed through all the 

 metamorphoses which our osseous fishes undergo, and 

 consequently that they are inferior to analogous species 

 of the present epoch, which have bony vertebras. Simi- 

 lar considerations apply to the fossil Crustacea and to the 

 fossil Echinoderms, when compared with the living ones, 

 and will probably be true of all classes of the Animal King- 

 dom, when fully studied as to their geological succession. 



