METAMORPHOSES OF ANIMALS. 181 



resolved by an examination of their anatoi-ical structure. 

 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 vertebrae. The middle part, 

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

 verse, and underneath the head ; and the caudal fin is un- 

 equally 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 inferior, 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 vertebrse become ossified, and its resemblance to the 

 Sturgeon is comparatively slight. As the Sturgeon has no 

 such transformation of the vertebrae, and is, in some sense, 

 arrested 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- _^^**--'- ^---':r^ 



phioxus, represented of its nat- ^^^^^^^^^^J^^^ 

 ural size, (Fig. 153.) not only Fig. 153. 



