[368] In _Grundriss einer Allgemeinen Naturgeschichte der Radiolarien_, Berlin, 1887, and _Kunstformen der Natur_, Suppl. Heft, Leipzig. [369] Haeckel had an intense admiration for Goethe's morphological work. It is a curious coincidence that the work of Goethe, Oken and Haeckel was closely associated with the town of Jena. [370] But he himself would not admit this! See _Gen. Morph._, ii., p. 11. [371] _Fuer Darwin_, 1864. Eng. trans, by Dallas as _Facts and Arguments for Darwin_, London, 1869. [372] The bion is the physiological, as the morphon is the morphological, individual. [373] See Vogt, _Embryologie des Salmones_, p. 259, 1842, and _supra_, p. 230. [374] _An Essay on Classification_, London, 1859. [375] It was hinted at by Tiedemann. "It is clear that, proceeding from the earlier to the more recent strata, a gradation in fossil forms can be established from the simplest organised animals, the polyps, up to the most complex, the mammals, and that accordingly the animal kingdom as a whole has its developmental periods just like the single individual organism. The species and genera which have become extinct during the evolutionary process may be compared with the organs which disappear during the development of the individual animal" (p. 73, 1808). [376] _The History of Creation_, vol. i., p. 310, 1876. Translation of the _Natuerliche Schoepfungsgeschichte_, 1868. [377] _Cf._ a parallel passage from Serres, _supra_, p. 82. [378] _Jenaische Zeitschrift_, ix., pp. 402-508, 1875. [379] _Loc. cit._, ix., p. 409. [380] _Untersuchungen zur vergl. Anatomie d. Wirbelthiere_, Leipzig, i., 1864; ii., 1865; and iii., 1872. [381] "U. d. Biologie in Jena waehrend des 19 Jahrhunderts," _Jenaische Zeitschrift_, xxxix., pp. 713-26, 1905. [382] _Grundriss der vergl. Anatomie_, 1874, 2nd ed., 1878. Trans. by F. Jeffrey Bell, revised by E. Ray Lankester, as _Elements of Comparative Anatomy_, London, 1878. [383] "This theory (evolution) shows that what was formerly called 'structural plan' or 'type' is the sum of the dispositions (_Einrichtungen_) of the animal organisation which are perpetuated by heredity, while it explains the modifications of these dispositions as adaptive states. Heredity and adaptation are thus the two important factors through which both the unity and the variety of organisation can be understood" (_Grundzuege_, p. 19). [384] _History of Creation_, i., pp. 241-2. [385] "On the use of the term Homology in Modern Zoology, and the distinction between Homogenetic and Homoplastic agreements," _Ann. Mag. Nat. Hist._ (4), vi., pp. 35-43, 1870. CHAPTER XV EARLY THEORIES ON THE ORIGIN OF VERTEBRATES