III.] INDEPENDENT SIMILARITIES OF STRUCTURE. 79 



learned Professor, refers to the structure of birds, and of 

 extinct reptiles more or less related to them. 



The class of birds is one which is remarkably uniform in 

 its organization. So much is this the case, that the best 

 mode of subdividing the class is a problem of the greatest 

 difficulty. Existing birds, however, present forms which, 

 though closely resembling in the greater part of their 

 structure, yet differ markedly the one from the other in 

 certain respects. One form is exemplified by the ostrich, 

 rhea, emeu, cassowary, apteryx, dinornis, &c. : these are the 

 strutMous birds. All other existing birds belong to the 

 second division, and are called (from the keel on the 

 breast-bone) carinate birds. 



Now birds and reptiles have such and so many points in 

 common, that Darwinians must regard the former as modified 

 descendants of ancient reptilian forms. But on Darwinian 

 principles it is impossible that the class of birds sp uniform 

 and homogeneous should have had a double reptilian origin. 

 If one set of birds sprang from one set of reptiles, and 

 another set of birds from another set of reptiles, the two 

 sets could never, by " Natural Selection " only, have grown 

 into such a perfect similarity. To admit such a pheno- 

 menon would be equivalent to abandoning the theory of 

 "Natural Selection" as the sole origin of species. 



Now, until recently it has generally been supposed by 

 evolutionists that those ancient flying reptiles, the ptero- 

 dactyles, or forms allied to them, were the progenitors of 

 the class of birds ; and certain parts of their structure 

 especially support this view. Eeference is here made to 

 the bladebone (scapula), and the bone which passes down 

 from the shoulder-joint to the breast-bone (viz. the cora- 

 coid). These bones are such remarkable anticipations of 



