How can we propose to draw up the inexhaustible inventory of all the manifestations of life, and why attempt to include all its species and their unknown varieties in narrow classes? Why say that there are only two modes of life, instinct on the one hand and intelligence on the other, "when we know how subtle and illusive is this Proteus, and that there are not two things only, but a thousand dissimilar things" (8/20.): or rather is it not always the same thing, everywhere present and acting in living matter, and susceptible of infinite degrees, under forms and disguises innumerable? This is why it escapes the "scalpel of the masters" and the apparatus of the chemists. We may dissect, we may scrutinize organs under the magnifying glass, examine wing-cases, count the nervures of the wings, the number of articulations in the limbs; we may reckon every point, like Réaumur forgetting not a line, not a hair; we may compare and measure every portion of the mouth, and define the class; and we shall not find a single point in all this physical architecture which will positively inform us of the habits of the insect. Of what account are a few slight differences? It is in the physical far more than in the anatomical differences that the inviolable demarcation between two species exists. Instincts dominate forms; the tool does not make the artisan; "and none of these various structures, however well adapted they may appear to us, bears within it its reason or its finality." Thus whatever opinion we may hold as to the nature of instinct, the accomplishments and habits of insects are not, properly speaking, connected with the external and visible form of their organs, and their acts do not necessarily presuppose the instruments which would be appropriate to them. We know that with most organisms, and particularly with plants, an almost imperceptible variation in material circumstances is often enough to modify their character and to produce fresh aptitudes. Nevertheless, we can but wonder, with Fabre, that physical modifications, which, when they do exist, are so slight always as to have escaped the most perfect observation, should have sufficed to determine the appearance of profoundly dissimilar faculties. Inexplicable abilities, unexpected habits, unforeseen physical aptitudes, and unheard-of industries are exercised by means of organs which are here and there practically identical. "The same tools are equally good for any purpose. Talent alone is able to adapt them to manifold ends." The Anthidia have two particular industries; "those which felt cotton and card the soft down of hairy plants have the same claws, the same mandibles, composed of the same portions as those which knead resin and mix it with fine gravel." (8/21.) The sloe-weevil "bores the hard stone of the sloe with the same rostrum as that which its congeners, so like it in conformation, employ to roll the leaves of the vine and the poplar into tiny cigars."