70 VERTEBRATE ZOOLOGY 



tongue" and its accessories. The claim is made that some of the 

 cranial cartilages are the rudiments of a former lower jaw. If the jaw- 

 less condition is secondary there is little reason for separating the 

 cyclostomes from the Pisces. A more nearly acceptable theory is that 

 the cyclostomes represent an early side line of vertebrate evolution 

 quite distinct from the true fishes. 



