342 



LAMARCK, HIS LIFE AND WORK 



that of amphibious mammals, which have given in 

 their turn origin to all the other mammals* 



" Indeed, the fishes having caused the formation 

 of Batrachia, and these of the Ophidian reptiles, both 

 having only one auricle in the heart, nature has 

 easily come to give a heart with a double auricle to 

 other reptiles which constitute two special branches ; 

 finally, she has easily arrived at the end of forming, 

 in the animals which had originated from each of 

 these branches, a heart with two ventricles. 



" Thus, among the reptiles whose heart has a double 

 auricle, on the one side, the Chelonians seem to have 

 given origin to the birds ; if, independently of several 

 relations which we cannot disregard, I should place 

 the head of a tortoise on the neck of certain birds, 

 I should perceive almost no disparity in the general 

 physiognomy of the factitious animal ; and on the 

 other side, the saurians, especially the ' planicaudes,' 

 such as the crocodiles, seem to have given, origin to 

 the amphibious mammals. 



" If the branch of the Chelonians has given rise to 

 birds, we can yet presume that the palmipede aquatic 

 birds, especially the brevipennes, such as the penguins 

 and the manchots, have given origin to the mono- 

 tremes. 



" Finally, if the branch of saurians has given rise 

 to the amphibious mammals, it will be most probable 

 that this branch is the source whence all the mam- 

 mals have taken their origin. 



" I therefore believe myself authorized to think 

 that the terrestrial mammals originally descended 

 from those aquatic mammals that we call Amphibia. 

 Because the latter being divided into three branches 

 by the diversity of the habits which, with the lapse of 

 time, they have adopted, some have caused the forma- 



* This sagacious, tliougli crude suggestion of tlie origin of birds 

 and mammals from tJie reptiles is now, after the lapse of nearly a 

 century, being confirmed by modern morphologists and palaaontologists. 



