Nana already appears--in her childhood and her youth--in the pages of "L'Assommoir," but Zola does not pass direct from that work to the later career of Gervaise's daughter. He first takes Gervaise's elder children, her sons by Lantier; and "L'Œuvre" (XIV) unfolds the painful story of Claude, the painter, a glimpse of whom has been given previously in "Le Ventre de Paris." Again in "L'Œuvre," one finds a record of downfall, but, whereas in "L'Assommoir" it has largely resulted from environment and circumstances, it now proceeds more directly from an evil heredity. Claude stands virtually on the border line that parts insanity from genius, and thus in his career, the old hypotheses of Moreau of Tours, and those subsequently enunciated in England by Nesbit, might find play. In the end, after a life of conflict and misery, insanity triumphs and Claude destroys himself. His tale, as one has stated previously, is linked with a picture of the French art-world. Fortunately a current of human interest flows through the book, for beside Claude the unhappy Christine, his wife, appears: she, like Gervaise, at first being a good, true, and courageous woman, one who commits the irremediable mistake of linking her life with that of a man fated to failure and insanity. In these last sections of Zola's series the march of degenerescence is hastened; downfall follows downfall; before long that of individuals is to be succeeded by a supreme collapse, that of the _régime_ under which they live. Thus, after "L'Œuvre," comes "La Bête Humaine" (XV), Claude's brother Jacques, an engine-driver, in whom a murderer appears among the Rougon-Macquarts. The hereditary virus, transmitted from Adélaïde Fouque, has turned in him to an insensate craving for woman's blood, and, frankly, his story is horrible. At the same time, while one follows the growth of his abominable disease, many a vivid page arrests attention: awful, yet a masterpiece of colloquial narrative and full of a penetrating psychology, is Severine's account of the murder of President Grandmorin; very human is Jacques' love for his engine, La Lison; and striking are the pictures of the snowstorm, the railway accident, and the death of Jacques and the stoker Pecqueux, at the end of the volume, when their train, crowded with soldiers, is seen rushing driverless, like some great, maddened, blind beast, towards catastrophe and annihilation.