METAMORPHOSES OF ANIMALS. 



149 



The White-fish has a skeleton, and moreover, a vertebral 

 column composed of firm bone. The Sturgeon (Fig. 152), 



Fig. 152. 



on the contrary, has no bone in the vertebral column, except 

 the spines or apophyses of the vertebra. The middle part, 

 or body of the vertebra, is cartilaginous ; the mouth is 

 transverse, and underneath the head ; and the caudal fin 

 is unequally forked, while in the White-fish it is equally 

 forked. 



384. If, however, we observe the young White-fish just 

 after it has issued from the egg (Fig. 123), the contrast will 

 be less striking. At this period the vertebrae are cartilagi- 

 nous, like those of the Sturgeon ; its mouth also is trans- 

 verse, and its tail undivided ; at that period the White-fish 

 and the Sturgeon are therefore much more alike. But this 

 similarity is only transient ; as the White-fish grows, its ver- 

 tebrae become ossified, and its resemblance to the Sturgeon 

 is comparatively slight. As the Sturgeon has no such 

 transformation of the vertebra, and is in some sense ar- 

 rested in its development, while the White-fish undergoes 

 subsequent transformation, we conclude that, compared with 

 the White-fish, it is really inferior in rank. 



385. This relative inferiority and superiority strikes us 

 still more, when we compare with our most perfect fishes 

 (the Salmon, the Cod) some of those worm-like animals, so 

 different from ordinary fishes that they were formerly placed 



among the worms. The Am- 

 phioxus, represented of its natu- 

 153. m l size (Fig. 153), not only 



has no bony skeleton, but not even a head, properly 



13* 



