GO KTIKNM: (;I:OITROY SAINT-IIILAIKK 



fishes that it reaches the maximum of its development" 



(P- 8 3 ). 



To sum up, the sternum in all four vertebrate classes is 



composed of the same elements, arranged ahvays in the 

 same way " One is ... led to the conception of an 

 ideal type of sternum for all Vertebrates, which then, 

 considered from a lower standpoint, resolves itself into 

 several secondary forms according as the whole or the 

 majority of the constituent materials are employed, or even 

 as these elements come to change their respective dimensions 

 or proportions" (p. 134). As to the elementary constituents, 

 "they give proof of individuality, and sometimes even, in 

 certain abnormalities, of independence, and rise to the level 

 of primary organisatory materials" (p. 132). What holds 

 good for the sternum holds good for other organs and 

 accordingly the unity of plan and composition can be 

 demonstrated for all the organs of Vertebrates. 



Soon after the publication of the Philosophie 

 auatouiiauc (1818) Geoffrey went further in his search for 

 unity, and maintained that the structure of insects and 

 Crustacea could be reduced to the vertebrate type. 



He proposed to replace Cuvier's classification of the 

 animal kingdom into the four large groups, Vertebrata, 

 Mollusca, Articulata, and Radiata by the following classifica- 

 tion : ] 



... , ( Hauts-Vertebres (Vcrtebrata, Cuv.). 



Vertebres , ^ . . ' ' 



tDermo-Vcrtebres (Articulata, Cuv.). 



., , I Mollusques (Mollusca, Cuv.). 

 Invertebres * , ' 



i Rayon nes (Radiata, Cuv.). 



The idea upon which is based the comparison of Articu- 

 lates with Vertebrates is that each skeletal segment of 

 Articulates is a vertebra. In the Hauts-vcrtebres the 

 vertcbiM- are internal; in the Dcrmo-vcrtebres they are 

 external. " /:rv/T animal /ires cither outside or inside its 

 vertebral column"- The essence of a vertebra is not its 

 form, nor its function, but its composition from four 



i "Snr unr . oloiinc vrert^bralc <-t ses c6tes dans Ics insectes 

 apiropodi . Acad. Set'., Kcl>. 12, iSso). Printed in his, pp. 5-7-5 2 > 

 i 



" Sur I'organisation des insi - tes," |. 45 s - /J/ X I'l 1 - 45 2 ' 6 - lS2 ( 2 )- 



