PRINCIPAL FAMILIES OF FISH. 35 



Oirrostomi. 



Only one species, the Amphioxus, is known of 

 this family, the lowest form in the scale of de- 

 velopment among fishes. In fact, it can hardly be 

 ranked as a vertebrate animal, as it appears to pos- 

 sess neither bones nor any of the usnal organs of 

 sense. 



n 2 



