20 



THE ANATOMY OF VERTEBKATED ANIMALS. 



onio condition of the axis of the tail, the superior and inferior 

 arches, and the interspinous bones, may be completely formed 

 in cartilage or bone. 



Whatever the condition of the extreme end of the spine 

 of a fish, it occasionally retains the same direction as the 

 trunk part, but is far more generally bent up, so as to form 



