"Behold in our stout and clumsy horses, habituated to draw heavy loads, and which constitute a special race by always being kept together--behold, I say, the difference in their form compared with those of English horses, which are all slender, with long necks, because for a long period they have been trained to run swiftly: behold in them the influence of a difference of habit, and judge for yourselves. You find them, then, such as they are in some degree in nature. You find there our cock and our hen in the condition we have [made] them, as also the mixed races that we have formed by mixed breeding between the varieties produced in different countries, or where they were so in the state of domesticity. You find there likewise our different races of domestic pigeons, our different dogs, etc. What are our cultivated fruits, our wheat, our cabbage, our lettuce, etc., etc., if they are not the result of changes which we ourselves have effected in these plants, in changing by our culture the conditions of their situation? Are they now found in this condition in nature? To these incontestable facts add the considerations which I have discussed in my _Recherches sur les Corps vivans_ (p. 56 _et suiv._), and decide for yourselves. "Thus, among living bodies, nature, as I have already said, offers only in an absolute way individuals which succeed each other genetically, and which descend one from the other. So the _species_ among them are only relative, and only temporary. "Nevertheless, to facilitate the study and the knowledge of so many different bodies it is useful to give the name of _species_ to the entire collection of individuals which are alike, which reproduction perpetuates in the same condition as long as the conditions of their situation do not change enough to make their habits, their character, and their form vary. "Such is, citizens, the exact sketch of that which goes on in nature since she has existed, and of that which the observation of her acts has alone enabled us to discover. I have fulfilled my object if, in presenting to you the results of my researches and of my experience, I have been able to disclose to you that which in your studies of this kind deserves your special attention. "You now doubtless conceive how important are the considerations which I have just exposed to you, and how wrong you would be if, in devoting yourself to the study of animals or of plants, you should seek to see among them only the multiplied distinctions that we have been obliged to establish; in a word, if you should confine yourselves to fixing in your memory the variable and indefinite nomenclature which is applied to so many different bodies, instead of studying Nature herself--her course, her means, and the constant results that she knows how to attain." On the next fly page are the following words: _Esquisse d'une Philosophie zoologique_.