122 ESSAY ON CLASSIFICATION 



is not found before the Lias; among Cephalopods we find the Nauti- 

 lus, but nothing like Orthoceras; Limulus, but nothing like Trilo- 

 bites. 



This study of the relations between the geographical distribution 

 of animals and their relative standing is rendered more difficult 

 and in many respects obscure by the circumstance that entire types, 

 characterized by peculiar structures, are so strangely limited in their 

 range; and yet even this shows how closely the geographical distri- 

 bution of animals is connected with their structure. Why New 

 Holland should have no Monkeys, no Carnivora, no Ruminants, no 

 Pachyderms, no Edentata, is not to be explained; but that this is 

 the case, every zoologist knows and is further aware that the Mar- 

 supials of that continental island represent, as it were, the other 

 orders of Mammalia, under their special structural modifications. 

 New Holland appears thus as a continent with the characters of an 

 older geological age. No one can fail therefore to perceive of how 

 great an interest for Classification will be a more extensive knowl- 

 edge of the geographical distribution of animals in general and of 

 the structural peculiarities exhibited by localized types. 



SECTION XXIX 

 MUTUAL DEPENDENCE OF THE ANIMAL AND VEGETABLE KINGDOMS 



Though it had long been known, by the experiments of de Saus- 

 5yj.gi46 lYi^i j-j^g breathing process is very different in animals and 

 plants and that while the former inhale atmospheric air and exhale 

 carbonic acid gas, the latter appropriate carbon and exhale oxygen, 

 it was not until Dumas and Boussingault^^^ called particularly the 

 attention of naturalists to the subject that it was fully understood 

 how direct the dependence is of the animal and vegetable kingdoms 

 one upon the other in that respect, or rather how the one consumes 

 what the other produces, and vice versa, thus tending to keep the 



"« [Horace Benedict de Saussure, 1740-1799.] 



"^Jean B. A. Dumas, "Lecon sur la statique chimique des etres organises," Annales 

 des Sciences Naturelles, VI (2d ser., 1836), 33, "Additions . . . ," in ibid., X\'I1 (2d ser., 

 1842), 122; Dumas and Jean B. J. Boussingault, "Recherches sur I'engraissement des 

 bestiaux et la formation du lait," in ibid., XIX (2d ser., 1843), 351. 



