[117]. O. Hertwig, ‘Das Problem der Befruchtung und der Isotropie des Eies.’ Jena, 1885.
[118]. This opinion was first expressed in my lecture, ‘Ueber die Dauer des Lebens,’ Jena, 1882, translated as the first essay in the present volume.
[119]. M. Nussbaum, ‘Sitzungber. der Niederrheinischen Gesellschaft fur Natur- und Heilkunde.’ Dec. 15, 1884.
[120]. A. Gruber, ‘Biologisches Centralblatt,’ Bd. IV. No. 23, and V. No. 5.
[121]. According to the observations of Nussbaum and van Beneden, the egg of Ascaris departs from the ordinary type, but I think that the latter observer goes too far when he concludes from the form of the nuclear spindle (of which the two halves are inclined to each other at an angle) that we have before us a process entirely different from that of ordinary nuclear division.
[122]. Trinchese, ‘I primi momenti dell’ evoluzione nei molluschi,’ Atti Acad. Lyncei (3) vii. 1879, Roma.
[123]. M. Nussbaum, ‘Archiv für Mikroskopische Anatomie,’ Bd. XVIII und XXIII.
[124]. Valaoritis, ‘Die Genesis des Thier-Eies.’ Leipzig, 1882.
[125]. Kölliker, ‘Die Bedeutung der Zellkerne,’ etc.; Zeitschr. f. wiss. Zool. Bd. XLII.
[126]. ‘Compt. rend.’ Tom. LIV. p. 150.