xix] 



GILL-SACS 



445 



tongue-bars. The external opening is circular; the connection 

 with the gullet, on the other hand, is a vertical slit (Fig. 219). 



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S*S 



cc ., 



P ,a 



rn c? os rH 



The whole set of sacs is supported on a framework of cartilage 

 which in its complete form as seen in the Lampreys, consists of 



