IV. _Lamarck's Views as published in 1806._[177] "Those who have observed much and have consulted the great collections, have been able to convince themselves that as gradually as the circumstances of their habitat, of exposure to their surroundings, of climate, food, mode of living, etc., have changed, the characters of size, form, of proportion between the parts, of color, of consistence, of duration, of agility, and of industry have proportionately changed. "They have been able to see, as regards the animals, that the more frequent and longer sustained use of any organ gradually strengthens this organ, develops it, enlarges it, and gives it a power proportional to the length of time it has been used; while the constant lack of use of such an organ insensibly weakens it, causes it to deteriorate, progressively diminishes its faculties, and tends to make it waste away.[178] "Finally, it has been remarked that all that nature has made individuals to acquire or lose by the sustained influence of circumstances where their race has existed for a long time, she has preserved by heredity in the new individuals which have originated from them (_elle le conserve par la génération aux nouveaux individus qui en proviennent_). These verities are firmly grounded, and can only be misunderstood by those who have never observed and followed nature in her operations. "Thus we are assured that that which is taken for _species_ among living bodies, and that all the specific differences which distinguish these natural productions, have no absolute _stability_, but that they enjoy only a relative _stability_; which it is very important to consider in order to fix the limits which we must establish in the determination of that which we must call _species_. "It is known that different places change in nature and character by reason of their position, their 'composition' [we should say geological structure or features], and their climate; that which is easily perceived in passing over different places distinguished by special characteristics; behold already a cause of variation for the natural productions which inhabit these different places. But that which is not sufficiently known, and even that which people refuse to believe, is that each place itself changes after a time, in exposure, in climate, in nature, and in character, although with a slowness so great in relation to our period of time that we attribute to it a perfect _stability_. "Now, in either case, these changed places proportionately change the circumstances relative to the living bodies which inhabit them, and these produce again other influences on those same bodies.