SUMMARY OF ' PHILOSOPHIE ZOOLOGIQUE: 267 



apparent immutability of species, that has been too 

 inconsiderately drawn.* 



"The analogies and points of agreement between 

 living organisms, are always incomplete when based 

 upon the consideration of any single organ only. But 

 though still incomplete, they will be much more impor- 

 tant according as the organ on which they are founded 

 is an essential one or otherwise. 



" With animals, those analogies are most important 

 which exist between organs most necessary for the con- 

 servation of their life. With plants, between their 

 organs of generation. Hence, with animals, it will be 

 the interior structure which will determine the most 

 important analogies : with plants it will be the manner 

 in which they fructify, f 



" With animals we should look to nerves, organs of 

 respiration, and those of the circulation; with plants, 

 to the embryo and its accessories, the sexual organs of 

 their flowers, &c. { To do this, will set us on to the 

 Natural Method, which is as it were a sketch traced 

 by man of the order taken by Nature in her produc- 

 tions^ Nevertheless the divisions which we shall be 

 obliged to establish, will still be arbitrary and arti- 

 ficial, though presenting to our view sections arranged 

 in the order which Nature has pursued. || 



" What, then," he asks, H " is species and can we 

 show that species has changed however slowly ? " He 

 now covers some of the ground since enlarged upon in 

 Mr. Darwin's second chapter, in which the arbitrary 



* ' Phil. Zool.,' torn. i. p. 62. t Page 63. J Page 64. 



Page 65. || Page 67. H Chap. iii. 



