Footnotes for Essay V.
[176]. C. Nägeli, ‘Mechanisch-physiologische Theorie der Abstammungslehre.’ München u. Leipzig, 1884.
[177]. ‘Ueber die Berechtigung der Darwin’schen Theorie.’ Leipzig, 1868, p. 27.
[178]. l. c., Preface, p. vi.
[179]. Since the above was written many other morphological peculiarities of plants have been rightly explained as adaptations. Compare, for instance, the investigations of Stahl on the means by which plants protect themselves against the attacks of snails and slugs (Jena, 1888).—A. W., 1888.
[180]. l. c., pp. 117, 286.
[181]. Compare the second and fourth of the preceding Essays, ‘On Heredity’ and ‘The Continuity of the Germ-plasm as the Foundation of a Theory of Heredity.’
[182]. Compare Rauber, ‘Homo sapiens ferus oder die Zustände der Verwilderten.’ Leipzig, 1885.
[183]. ‘Sitzungsberichte der baierischen Akademie der Wissenschaften,’ vom 18 Nov. 1865. Compare also his ‘Mechanisch-physiologische Theorie der Abstammungslehre,’ p. 102, etc.
[184]. Jordan, ‘Remarques sur le fait de l’existence en société des espèces végétales affines.’ Lyon, 1873.
[185]. S. Hermann’s ‘Handbuch der Physiologie,’ Theil II; ‘Physiologie der Zeugung,’ by V. Hensen.
[186]. E. van Beneden, ‘Recherches sur la maturation de l’œuf, la fécondation et la division cellulaire.’ Gand u. Leipzig, 1883, pp. 404 et seq.
[187]. Rolph, ‘Biologische Probleme.’ Leipzig, 1882.
[188]. Cienkowsky, ‘Arch. f. mikr. Anat.,’ ix. p. 47. 1873.
[189]. Hensen, ‘Physiologie der Zeugung,’ p. 139.
[190]. Coalescence takes place in the so-called bud-like conjugation of Vorticellidae and Trichodinidae, etc.
[191]. Compare (1) Bardeleben, ‘Zur Entwicklung der Fusswurzel,’ Sitzungsber. d. Jen. Gesellschaft, Jahrg. 1885, Feb. 6; also ‘Verhandl. d. Naturforscherversammlung zu Strassburg,’ 1885, p. 203; (2) G. Baur, ‘Zur Morphologie des Carpus und Tarsus der Wirbelthiere,’ Zool. Anzeiger, 1885, pp. 326, 486.
[192]. In frogs the sixth toe exists in the hind legs as a rudimentary prehallux. Compare Born, Morpholog. Jahrbuch, Bd. I, 1876.
[193]. I here make use of the same illustration which I employed in my first attempt to explain the effects of panmixia. Compare the second Essay ‘On Heredity.’
[194]. [E. Ray Lankester has suggested (Encycl. Britann., art. ‘Zoology,’ pp. 818, 819) that the blindness of cave-dwelling and deep-sea animals is also due to the fact that ‘those individuals with perfect eyes would follow the glimmer of light and eventually escape to the outer air or the shallower depths, leaving behind those with imperfect eyes to breed in the dark place. A natural selection would thus be effected.’ Such a sifting process would certainly greatly quicken the rate of degeneration due to panmixia alone.—E. B. P.]
[195]. Adler, ‘Zeitschrift f. wiss. Zool.,’ Bd. XXXV, 1881.
[196]. Compare my paper, ‘Parthenogenese bei den Ostracoden,’ in ‘Zool. Anzeiger,’ 1880, p. 82. Purely negative evidence, unless on an immense scale, is quite rightly considered to be of no great value in most cases. But the condition of these animals renders the accumulation of such evidence unusually easy, because the presence of males in a colony of Ostracodes can be proved by a very simple indirect test. Thus if a colony contains any males the receptacula seminis of all mature females are filled with spermatozoa, and on the other hand we may be quite sure that males are absent, if after the examination of many mature females, no spermatozoa can be found in any of their receptacula.
[197]. We cannot, however, be absolutely certain of this, for it is conceivable that males may still occur in colonies other than those examined.
[198]. It has now been shown by Blochmann that males appear for a very short time towards the close of summer, as in the case of Phylloxera.—A. W., 1888.