number which possessed the same degree of organisation as the duckbills of to-day, now represented by only a few species; a supposition which the adherents of the theory of evolution made twenty-five years ago. I do not know that the pedigrees of the heroes of Homer have been so well preserved! In many other directions, however, speculation of late years in Germany has considerably digressed from the facts of experience and from all probability; especially with reference to the questions of propagation, variation, and heredity. Here, first of all, are to be mentioned the works of Weismann, _Ueber die Continuität des Keimplasmas_ (1885), _Die Bedeutung der sexuellen Fortpflanzung für die Selectionstheorie_ (1886), _Der Rückschritt in der Natur_ (1886), _Die Bedeutung der Richtungskörperchen für die Vererbungstheorie_ (1887), _Die Hypothese der Vererbung von Verletzungen_ (1889), and _Ueber Amphimixis_ (1891). If we revert to the beginnings of this movement we shall find that it is intimately connected with the more exact study of the processes of fecundation as perfected through the researches of Strassburger, the Hertwigs, and other investigators. In connection with the ideas of Nägeli concerning the so-called idioplasm, the notion was reached that the matter determinative of heredity was contained in the nucleoli, and that by the union of the paternal and maternal nucleoli the sum-total of the parental hereditary tendencies is transmitted to the offspring. This view was to a certain degree verified by the experiments of the brothers Hertwig in removing the nucleoli of the eggs of the sea-urchin; the result being that eggs containing the nucleoli alone, furnished, through artificial impregnation, results resembling the female parent, whereas eggs from which the nucleoli had been removed, furnished germs completely corresponding to the traits of the male parent.