The YOifHG HATtfRAMST: 



A Monthly Magazine of Natural History. 



Paet 98. FEBBUAKY, 1888. Vol. 9. 



EVOLUTION.— REPTILES AND BIRDS * 



By LINNAEUS GREENING. 



IN considering the evidence in support of the evolutionary theory which 

 is revealed to us by the study of reptiles and birds, the most obvious 

 is the fact that all reproduce by eggs. As all vertebrates below reptiles re- 

 produce by eggs, and of the higher ones, the monotremes (as Platypus and 

 Echidna) also, we may fairly take this fact as a connecting link between the 

 highest and the lowest vertebrates. The embryonic developments of the 

 sauropsidans would be too abstruse a subject for a sketch of this kind, but I 

 may mention one fact tending to show the common origin of these creatures, 

 and that is, that in the earliest stages of development the tails of all birds are 

 distinctly reptilian in character ; that is to say, there is no coalescence of the 

 last caudal vertebrae, as in the existing adult birds, but each vertebra is 

 separate and distinct, as in the existing reptiles and in some fossil birds. It 

 is difficult to realize any relationship between creatures apparently so unlike 

 as the slow moving tortoise and the swift flying falcon, the ponderous crocodile 

 and the nimble lizard. It is well to remember that all reptiles and birds are 

 classed together as Sauropsida, for widely as they differ, all present certain 

 striking anatomical and functional resemblances, which clearly separate them 

 from the Ichthyopsida on the one side arid the Mammals on the other. 



Without going into minute anatomical details, it will suffice to point out 

 two or three leading sauropsidan characteristics. In all, the skull articulates 

 with the vertebral column by a single articulating surface or condyle ; and 

 each half or ramus of the lower jaw is composed of several pieces, and articu- 

 lates with the skull, not directly, but by the intervention of a peculiar bone 

 called the quadrate. A simple illustration of this similarity of structure may 

 be obtained by any one who will be at the trouble of procuring and examin- 



*Read before the Warrington Field Club, Nov. 12th, 1886. 



