PROGRESS OF ANIMAL MORPHOLOGY. 491 



best physiologists, as explaining the distribution of 

 the nerves, and other phenomena. Spix further 

 extended the application of the vertebral theory 

 to the heads of all classes of vetebrate animals; and 

 Bojanus published a Memoir expressly on the ver- 

 tebral structure of the skulls of fishes in Oken's 

 Isis for 1818. Geoffroy Saint-Hilaire presented 

 a lithographic plate to the French Academy in 

 February 1824, entitled Composition de la Tdte 

 osseuse chez I'Homme et Les Animaux, and deve- 

 loped his views of the vertebral composition of the 

 skull in two Memoirs published in the Annales des 

 Sciences Naturelles for 1824. We cannot fail to 

 recognize here the attempt to apply to the skeleton 

 of animals the principle which leads botanists to 

 consider all the parts of a flower as transforma- 

 tions of the same organs. How far the application 

 of the principle, as here proposed, is just, I must 

 leave philosophical physiologists to decide. 



By these and similar researches, it is held by the 

 best physiologists that the skull of all vertebrate 

 animals is pretty well reduced to a uniform structure, 

 and the laws of its variations nearly determined 7 . 



The vertebrate animals being thus reduced to a 

 single type, the question arises how far this can be 

 done with regard to other animals, and how many 

 such types there are. And here we come to one of 

 the important services which Cuvier rendered to 

 natural history. 



? Cuv. Hist. Sc. Nat. iii. 442. 



