GEOFFROY ST. HILATRE. Ti 
the transformation of animal and vegetable species was less 
effected by the action of the organism itself (by habit, 
practice, use, or disuse of organs) than by the “monde 
ambiant,” that is, by the continual change of the outer 
world, especially of the atmosphere. He conceives the 
organism as passive, in regard to the vital conditions of the 
outer world, while Lamarck, on the contrary, regards it 
as active. Geoffroy thinks, for example, that birds origi- 
nated from lizard-like reptiles, simply by a diminution of 
the carbonic acid in the atmosphere, in consequence of which 
the breathing process became more animated and energetic 
through the increased proportion of oxygen in the atmosphere. 
Thus there arose a higher temperature of the blood, an 
increased activity of the nerves and muscles, and the scales 
of the reptiles became the feathers of the birds, ete. This 
conception is based upon a correct thought, but although 
the change of the atmosphere, as wellas the change of every 
other external condition of existence, certainly effects 
directly or indirectly the transformation of the organism, 
yet this single cause is by itself too unimportant for such 
effects to be ascribed to it. It is even less important than 
practice and habit, upon which Lamarck lays too much 
stress. Geoffroy’s chief merit consists in his having vindi- 
cated the monistic conception of nature, the unity of 
organic forms, and the deep genealogical connection of the 
different organic types in the face of Cuvier’s powerful 
influence. I have already mentioned in the preceding 
chapter (pp. 87, 88) the celebrated disputes between the two 
great opponents in the Academy of Paris, especially the 
fierce conflicts on the 22nd of February, and on the 19th of 
July, in which Goethe took so lively an interest. On that 
