80 THE GENESIS OF SPECIES. [CHAP. 



the same parts in ordinary (i.e. carinate) birds, that it is 

 hardly possible for a Darwinian not to regard the resem- 

 blance as due to community of origin. This resemblance 

 was carefully pointed out by Professor Huxley in his 

 " Hunterian Course" for 1867, when attention was called 

 to the existence in Dimorphodon macronyx of even that 

 small process which in birds gives attachment to the upper 

 end of the merrythought. Also Mr. Seeley l has shown 

 that in pterodactyles, as in birds, the optic lobes of the 

 brain were placed low down on each side "lateral and 

 depressed," and that several details of cranial structure were 

 remarkably avian. Nevertheless, the view has been put 

 forward and ably maintained by Professor Huxley, 2 as 

 also by Professor Cope in the United States, that the line 

 of descent from reptiles to birds has not been from ordinary 

 reptiles, through pterodactyle-like forms, to ordinary birds, 

 but to the struthious ones from certain extinct reptiles 

 termed Dinosauria ; one of the most familiarly known of 

 which is the Iguanodon of the Wealden formation. In 

 these Dinosauria we find skeletal characters unlike those 

 of ordinary (i.e. carinate) birds, but closely resembling in 

 certain points the osseous structure of the struthious birds. 

 Thus a difficulty presents itself as to the explanation of 

 the three following relationships : (1) That of the Ptero- 

 dactyles with carinate birds ; (2) that of the Dinosauria 

 with struthious birds ; (3) that of the carinate and 

 struthious birds with each other. 



1 See "Ann. and Mag. of Nat. Hist." for August 1870, p. 140 ; and for 

 January 1871, p. 20, plates ii. and iii. 



2 See "Proceedings of the Royal Institution," vol. v. part iv. p. 278 : 

 Report of a Lecture delivered February 7, 1868. Also " Quarterly Journal 

 of the Geological Society," February 1870 : "Contributions to the Anatomy 

 and Taxonomy of the Dinosauria." 



