CHAPTER VIII 



THE BONY FISHES 



Though this chapter is broadly entitled 'The Bony 

 Fishes,' it is not our intention to add to the evolutionary 

 history of the fresh-water forms, but rather to consider 

 the fishes that live in the sea. In a sense, the following 

 discussion is a detour both in the progress of our story 

 and in the actual evolution of the vertebrates: we are in 

 the position of the motorist who, when he found him- 

 self at the end of a road in the Tennessee mountains, 

 inquired at a hillside cabin how he could get to Nash- 

 ville; and was told, after considerable cogitation, "Mis- 

 ter, if I wanted to get to Nashville, I wouldn't start from 

 here," The point is, that though it was no mean task 

 for the bony fishes to invade the sea in the first place, 

 having done so they found themselves in a bhnd alley 

 which did not admit of any great evolutionary advance. 



Nevertheless, the marine fishes are of interest in them- 

 selves, for several reasons. They afford a substantial frac- 

 tion of the world's food supply, a no mean consideration. 

 They have also afforded us one of the most interesting 

 chapters in the comparative physiology and anatomy of 

 the kidney. It was the study of the marine fishes that 

 led to the discovery of the aglomerular kidney, and in- 

 directly to a better knowledge of how the kidney works 

 in antecedent glomeiiilar forms; and these studies, in 



