45 6 



The Evolution of Fishes 



herring and salmon extends through the characins to the loach, 

 carps, catfishes, and electric eel. The fishes of this series have 

 the anterior vertebrae coossified and modified in connection with 

 the hearing organ, a structure not appearing elsewhere among 

 fishes. This group includes the majority of fresh-water fishes. 



FIG. 269. Fish with jugular ventral fins, Bassozetus catena Goode & Bean. 

 Family Brotulidcc. Gulf Stream. 



Still another great group, the eels, have lost the ventral fins 

 and the bones of the head have suffered much degradation. 



The most highly developed fishes, all things considered, are 

 doubtless the allies of the perch, bass, and sculpin. These fishes 



FIG. 270. A specialized bony fish, Trachicephalus uranoscopus. Family Scor- 

 pcenidce. From Swatow, China. 



have lost the air-duct and on the whole they show the greatest 

 development of the greatest number of structures. In these 

 groups their traits one after another are carried to an extreme 

 and these stages of extreme specialization give way one after 

 another to phases of degeneration. The specialization of one 



