80 THE GENESIS OF SPECIES. [Chap. 



the same parts in ordinary {i.e. carinate) birds, tliat it is 

 liardly possible for a Darwinian not to regard tlie resem- 

 blance as due to community of origin. This resend dance 

 Mas carefully i)ointed out by Professor Huxley in his 

 " Hunterian Course" for 18G7, when attention was called 

 to tlio existence in Dimorjihodon macronyx of even that 

 small pi'ocess which in birds gives attachment to the upper 

 end of the merrythought. Also jMr. Seeley ^ has shown 

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

 brain were placed low down on each side — " latend 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,- as 

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

 of descent from reptiles to birds has not been from ordinaiy 

 rei)tiles, through pterodactyle-like forms, to ordinary l)irds, 

 but to the struthious ones from certain extinct reptiles 

 termed Dinosauiia ; 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 

 cet'tain points the osseous structure of the struthious l)irds. 

 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 stnithious birds; (3) that of the carinate and 

 struthious lurds with each other. 



1 Sec "Ami. and Ma.^r. of Nat. Hist." for Augii.st 1S70, i>. 140 ; and for 

 Jamiary 1871, \>. 20, plates ii. and iii. 



2 See "Proceeding's of the IJoyal Institution," vol. v. part iv. p. 278: 

 Report of a Lecture delivort d February 7, 1868, Also " Quarterly Journal 

 of the Geological Society," Fehruary 1S70 : "(.'ontrilmtions to the Anatomy 

 and Taxonomy of the Dinosiiuria." 



