(6) Formation of a second polar cell in the same manner as the first, part of the spindle still remaining in the egg.
(7) Conversion of the part of the spindle remaining in the egg into a nucleus—the female pronucleus.
(8) Transportation of the female pronucleus towards the centre of the egg.
(9) Entrance of one spermatozoon into the egg.
(10) Conversion of the head of the spermatozoon into a nucleus—the male pronucleus.
(11) Appearance of radial striæ round the male pronucleus, which gradually travels towards the female pronucleus.
(12) Fusion of male and female pronuclei to form the first segmentation nucleus.
(76) Auerbach. Organologische Studien, Heft 2. Breslau, 1874.
(77) Bambeke. “Recherches s. Embryologie des Batraciens.” Bull. de l’Acad. royale de Belgique, 2me Sér., T. LXI., 1876.
(78) E. van Beneden. “La Maturation de l’Œuf des Mammifères.” Bull. de l’Acad. royale de Belgique, 2me Sér., T. XL. No. 12, 1875.
(79) Idem. “Contributions à l’Histoire de la Vésicule Germinative, &c. ” Bull. de l’Acad. royale de Belgique, 2me Sér., T. XLI. No. 1, 1876.
(80) O. Bütschli. Eizelle, Zelltheilung, und Conjugation der Infusorien. Frankfurt, 1876.
(81) F. M. Balfour. “On the Phenomena accompanying the Maturation and Impregnation of the Ovum.” Quart. J. of Micros. Science, Vol. XVIII., 1878.
(82) Calberla. “Befruchtungsvorgang beim Ei von Petromyzon Planeri.” Zeit. f. wiss. Zool., Vol. XXX.
(83) W. Flemming. “Studien in d. Entwickelungsgeschichte der Najaden.” Sitz. d. k. Akad. Wien, B. LXXI., 1875.
(84) H. Fol. “Die erste Entwickelung des Geryonideneies.” Jenaische Zeitschrift, Vol. VII., 1873.
(85) Idem. “Sur le Développement des Ptéropodes.” Archives de Zoologie Expérimentale et Générale, Vol. IV. and V. 1875‑6.
(86) Idem. “Sur le Commencement de l’Hénogénie.” Archives des Sciences Physiques et Naturelles. Genève, 1877.
(87) Idem. Recherches s. l. Fécondation et l. commen. d. l’Hénogénie. Genève, 1879.
(88) R. Greeff. “Ueb. d. Bau u. d. Entwickelung d. Echinodermen.” Sitzun. der Gesellschaft z. Beförderung d. gesammten Naturwiss. z. Marburg, No. 5, 1876.
(89) Oscar Hertwig. “Beit. z. Kenntniss d. Bildung, &c., d. thier. Eies.” Morphologisches Jahrbuch, Vol. I., 1876.
(90) Idem.Ibid. Morphologisches Jahrbuch, Vol. III. Heft 1, 1877.
(91) Idem. “Weitere Beiträge, &c.” Morphologisches Jahrbuch, Vol. III., 1877, Heft 3.
(92) Idem. “Beit. z. Kenntniss, &c. ” Morphologisches Jahrbuch, Vol. IV. Heft 1 and 2, 1878.
(93) N. Kleinenberg. Hydra. Leipzig, 1872.
(94) C. Kupffer u. B. Benecke. Der Vorgang d. Befruchtung am Eie d. Neunaugen. Königsberg, 1878.
(95) J. Oellacher. “Beiträge zur Geschichte des Keimbläschens im Wirbelthiere.” Archiv f. mikr. Anat., Bd. VIII., 1872.
(96) W. Salensky. “Befruchtung u. Furchung d. Sterlets-Eies.” Zoologischer Anzeiger, No. 11, 1878.
(97) E. Selenka. Befruchtung des Eies von Toxopneustes variegatus. Leipzig, 1878.
(98) Strasburger. Ueber Zellbildung u. Zelltheilung. Jena, 1876.
(99) Idem. Ueber Befruchtung u. Zelltheilung. Jena, 1878.
(100) C. O. Whitman. “The Embryology of Clepsine.” Quart. J. of Micr. Science, Vol. XVIII., 1878.
[28] By the term ‘nuclear spindle’ I refer to the peculiar form of a double striated cone assumed by the nucleus just before division, which is no doubt familiar to all my readers. I use the term star for the peculiar stellate figure usually visible at the poles of the nuclear spindle. For a further description of these parts the reader is referred to Chapter IV.
[29] For the further details on the nuclear spindle vide the next Chapter.