count fifty species in Europe. More than a hundred have been found by Heer, of Zurich, and Mayr, of Vienna, in the cantons of Oeningen and Radoboj alone; several seem identical with existing species. Most of them have wings; these are males and females. Workers are rare; and that is explained by the nature of the rock, deposited at the bottom of still waters. The winged insects fell into it by thousands; the workers, more lowly in existence, attached to earth, have left fewer victims in the streams that preserve the record of that age. For the same reason, those sepulchres, so rich in species, teach us nothing of the habits or abodes of the ants of that time. What we do know is, that there were also plant-lice in the country, and that the larvæ of phryganes made for themselves even then, as they do now, those cases in which they live, and which they carry about everywhere with them. Some of these have been found at Oeningen. We have butterflies' wings of that era with their marks, if not with their coloring. Who knows whether we shall not some day discover a wasps'-nest dropped from a bough, and a trifle less regular than those of to-day? Even were it just as perfect, that would in nowise weaken the hypothesis of progressive development in the instinct by which it was built. Should we not have, beyond the Jurassic epoch, an enormous past, beside which the actual age now of the deposits of Oeningen and Radoboj is, perhaps, like a day or an hour in the history of man?
The grand result which the introduction of Darwin's ideas into biological science has had is, beyond question, to have transformed a subject hitherto deemed unapproachable and insolvable into a question of development that may be attacked by our investigations. Instinct, like the outward forms of animals, has always been made dependent on those first causes too high for man to raise his look to them. The observations of the English naturalist have brought the problem upon new ground; his logic, his science, have forced the world to accept at last the ideas formerly defended by Cuvier's opponents, by Lamarck and Geoffroy Saint-Hilaire. The doctrine of the immutability of animal forms has had its time, and that of the invariability of instinct is falling into ruin. Darwin proves, in fact, that it suffices to admit the principle of intelligence, which no one now denies to animals, and then the twofold influence of habit and hereditary tendency, and last that law, stated by himself, of absorption of the poorly-endowed races by these better endowed, to reach the conclusion that the finely-perfected instinct of the bee or the ant is nothing more than a purely natural phenomenon, a necessary consequence of life. The most complex instinct is merely an hereditary accumulation of very simple habits, of which the first source was always in the spontaneous intelligence of the individual. Instinct, then, including that of neuter animals, may be defined, "a group of habits, slowly acquired, and fixed by inheritance." Then it appears to us as independent, in some degree, of the forms of the animal; the variations it presents find their explanation;
