Again Galton states—‘Out of the structureless ovum the embryonic elements are taken ... and these are developed (_a_) into the visible adult individual; on the other hand ..., after the embryonic elements have been segregated, the large residue is developed (_b_) into the latent elements contained in the adult individual.’ The above quoted sentences and diagram indicate that Galton does not derive the whole of the hereditary tendencies from the latent elements, but that he believes some effect is also produced by the patent elements. When however he contrasts the relative power of these two influences, he attaches comparatively little importance to the patent elements. Thus if any character be fixed upon, Galton states that it ‘may be conceived (1) as purely personal, without the concurrence of any latent equivalents, (2) as personal but conjoined with latent equivalents, and (3) as existent wholly in a latent form.’ He argues that the hereditary power in the first case is exceedingly feeble, because ‘the effects of the use and disuse of limbs, and those of habit, are transmitted to posterity in only a very slight degree.’ He also argues that many instances of the supposed transmission of personal characters are really due to latent equivalents. ‘The personal manifestation is, on the average, though it need not be so in every case, a certain proof of the existence of latent elements.’ Having argued that the strength of the latter in heredity is further supported by the facts of reversion, Galton considers it is safe to conclude ‘that the contribution from the patent elements is very much less than from the latent ones.’ In the later development of his theory, Galton adheres to the conception of ‘gemmules’ and accepts Darwin’s views, although ‘with considerable modification.’ Together with pangenesis itself, Galton’s theory must be looked upon as _preformational_, and so far it is in opposition to Weismann’s theory which is _epigenetic_. See Appendix IV. to the next Essay (V.), pp. 316-319.—E. B. P.] Footnote 104: Nägeli, ‘Mechanisch-physiologische Theorie der Abstammungslehre.’ München u. Leipzig, 1884. Footnote 105: O. Hertwig, ‘Beiträge zur Kenntniss der Bildung, Befruchtung und Theilung des thierischen Eies.’ Leipzig, 1876. Footnote 106: Fol, ‘Recherches sur la fécondation, etc.’ Genève, 1879. Footnote 107: Kölliker formerly stated, and has again repeated in his most recent publication, that the spermatozoa (‘Samenfäden’) are mere nuclei. At the same time he recognizes the existence of sperm-cells in certain species. But proofs of the former assertion ought to be much stronger in order to be sufficient to support so improbable a hypothesis as that the elements of fertilization may possess a varying morphological value. Compare Zeitschr. f. wiss. Zool., Bd. XLII. Footnote 108: F. M. Balfour, ‘Comparative Embryology,’ vol. i. p. 69.