172 



THE CHAIN OF LIFE. 



need, to swim ; while they could probably perch like birds on 

 rocks and trees, Their heads, though very lightly framed, were 

 large and reptilian in aspect, and furnished with sharp teeth, 

 and sometimes probably with a beak as well. Few creatures 

 of the old world are of more hideous and sinister aspect. 

 There are many species, most of them small, but some of 

 those in the later Mesozoic attained to so great a size that 

 the expanse of their wings must have exceeded twenty feet, 

 making them veritable flying dragons, probably formidable to 

 all the smaller animals of their time. Though these animals 



Fig. 148. — A Jurassic Bird {/irchaopteryx macroura). — After Owen. 



were strictly reptiles, they combined in their structures contri- 

 vances for aerial locomotion now distributed between the bp.ts 

 and the birds. They had bat-like wings and bird-like chests. 

 Some had horny beaks. All had hollow limb bones, and air 

 cavities to give lightness to the skull. Their brains approach 

 to those of birds, and, as already stated, their respiration and 

 circulation must have been of a high order. These facts are 

 very suggestive, and perhaps in no point is tl.e imagination or 

 the faith of the devout evolutionist more severely tested than 

 in realising the spontaneous assumption of these characters by 



