Shortly after the Franco-Prussian War, Edouard Piette (b. 1827, d. 1906), who had held the office of magistrate in various towns in the departments of Ardennes and Aisne, France, and who was already distinguished for his general scientific attainments, began to devote himself especially to the evolution of art in Upper Palæolithic times, and assembled the great collections which are described and illustrated in his classic work, _L'Art pendant l'Age du Renne_ (1907).(32) He first established several phases of artistic evolution in the Magdalenian stage, and only recognized in his later years the station of Brassempouy, not comprehending that the Aurignacian art which he found there underlay the Solutrean culture and was separated by a long interval of time from the most ancient Magdalenian. His distinct contribution to Palæolithic history is his discovery of the _Étage azilien_ overlying the Magdalenian in the cavern of Mas d'Azil. [Illustration: FIG. 4. Evolution of the lance-point, spear, or dart head. Note the increasing symmetry and skill in the flaking and retouch as the types pass in ascending order through the Chellean, Acheulean, Mousterian, and Aurignacian, into the perfected, symmetrical, double-pointed 'laurel-leaf' of the Solutrean; and into the subsequent decline in the flint industry of the Magdalenian and Azilian stages. After de Mortillet, Obermaier, and Hoernes.] Henri Breuil, a pupil of Piette and of Cartailhac, exploring during the decade, 1902-12, chiefly under the influence of Cartailhac, formed a clear conception of the whole Upper Palæolithic and its subdivisions, and placed the Aurignacian definitely at the base of the series. Thus step by step the culture stages of archæological evolution have been established and may be summarized with the type stations as follows: ÉTAGE STATION Tardenoisien, Fère-en-Tardenois, Aisne. Azilien, Mas d'Azil, Ariège. Magdalenien, La Madeleine, près Tursac, Dordogne. Solutréen, Solutré près Mâcon, Saône-et-Loire. Aurignacien, Aurignac, Haute-Garonne. Moustérien, Le Moustier, commune de Peyzac, Dordogne. Acheuléen, St. Acheul, près Amiens, Somme. Chelléen, Chelles-sur-Marne, Seine-et-Marne. Pre-Chelléen (= Mesvinien, Rutot), Mesvin, Mons, Belgique. These stages, at first regarded as single, have each been subdivided into three or more substages, as a result of the more refined appreciation of the subtle advances in Palæolithic invention and technique. [Illustration: FIG. 5. The type stations of the successive stages of Palæolithic culture from the Chellean to the Azilian-Tardenoisian.]