Although his physical forces are failing him, although his limbs falter, his brain remains intact, and is giving us its last fruit in his studies on the Cabbage caterpillar and the Glow-worm, which mark a sudden rejuvenescence of thought on his part, and the commencement of a new cycle of studies, which promise to be of the greatest originality. To him the animal world has always been full of dizzy surprises, and the insects led him "into a new and barely suspected region, which is ALMOST ABSURD." (16/6.) The glow-worms, motionless on their twigs of thyme, light their lamps of an evening, in the cool of the beautiful summer nights. What do these fires signify? How explain the mystery of this phosphorescence? Why this slow combustion, "this species of respiration, more active than in the ordinary state"? and what is the oxidizable substance "which gives this white and gentle luminosity"? Is it a flame of love like that which lights the Agaric of the olive-tree "to celebrate its nuptials and the emission of its spores"? But what reason can the larva have for illuminating itself? Why is the egg, already enclosed in the secrecy of the ovaries, already luminous? "The soft light of the Agaric has confounded our ideas of optics; it does not refract, it does not form an image when passed through a lens, it does not affect ordinary photographic plates." (16/7.) But here are other miracles: "Another fungus, the Clathrix, with no trace of phosphorescence, affects photographic plates almost as quickly as would a ray of sunlight. The Clathrix tenebrosa does what the Agaricus olearius has no power to do." (16/8.) And if the beacon of the Glow-worm recalls the light of the Agaric, the Clathrix reminds us of another insect, the Greater Peacock moth. In the obscurity of a dark chamber this splendid moth emits phantasmal radiations, perhaps intermittent and reserved for the season of nuptials, signals invisible to us, and perceptible only to those children of the night, who may have found this means to communicate one with another, to call one another in the darkness, and to speak with one another. (16/9.) Such are the interesting subjects which only yesterday were occupying this great worker; the occult properties, the radiant energies of organic matter; of phosphorescence, of light, the living symbols of the great universal Eros.