"This propensity of animals to preserve their habits and to renew the actions resulting from them being once acquired, is then propagated by means of reproduction or generation, which preserves the organization and the disposition of parts in the state thus attained, so that this same propensity already exists in the new individuals even before they have exercised it. "It is thus that the same habits and the same _instinct_ are perpetuated from generation to generation in the different species or races of animals, without offering any notable variation,[188] so long as it does not suffer change in the circumstances essential to the mode of life." "_On the Industry of Certain Animals._ "In those animals which have no brain that which we call _industry_ as applied to certain of their actions does not deserve such a name, for it is a mistake to attribute to them a faculty which they do not possess. "Propensities transmitted and received by heredity (_génération_); habits of performing complicated actions, and which result from these acquired propensities; finally, different difficulties gradually and habitually overcome by as many emotions of the organic sense (_sentiment intérieur_), constitute the sum of actions which are always the same in the individuals of the same race, to which we inconsiderately give the name of _industry_. "The instinct of animals being formed by the habit of satisfying the four kinds of wants mentioned above, and resulting from the propensities acquired for a long time which urge them on in a way determined for each species, there comes to pass, in the case of some, only a complication in the actions which can satisfy these four kinds of wants, or certain of them, and, indeed, only the different difficulties necessary to be overcome have gradually compelled the animal to extend and make contrivances, and have led it, without choice or any intellectual act, but only by the emotions of the organic sense, to perform such and such acts. "Hence the origin, in certain animals, of different complicated actions, which has been called _industry_, and which are so enthusiastically admired, because it has always been supposed, at least tacitly, that these actions were contrived and deliberately planned, which is plainly erroneous. They are evidently the fruit of a necessity which has expanded and directed the habits of the animals performing them, and which renders them such as we observe. "What I have just said is especially applicable to the invertebrate animals, in which there enters no act of intelligence. None of these can indeed freely vary its actions; none of them has the power of abandoning what we call its _industry_ to adopt any other kind.