The Skull 



1^3 



it brings vividly to iniiul the image of an animal which 

 muit have once existed — a hsli-like creature with no 

 jaw?, btit with a gristly mass which held up and pro- 

 tected the delicate blood-fringes, or gills, b}' means of 

 which all true fishes breathe. 



Our shark is a very convenient starting-point, and 

 before going further we should mention the technical name 



Fig. S7.— Gill-bars of Shark. 



of this grouj) — Eln<rnnJrrn/irJ:s. or strap-gilled fishes. 

 There are usually five of these gills, and within each 

 strap or fold of skin is a jointed arch of gristle. 



AU this mav l)e verv true, sav vou, btit what bearing 



* V »■ * 



has it on the skull of the chicken? 



We have seen that in sharks the number of gills has 

 Ijeen greatly reduced, and a i)air of very loosely attached 

 jaws has been acquired.— and the truth gradually dawns 



