[147]. Van Beneden, even in his last work, considers these bodies to have only the value of nuclei; l. c., p. 394.
[148]. I purposely abstain from using a more precise term, for the complicated terminology employed in spermatogenesis hardly contributes anything to the elucidation of the phenomena themselves. Why do we not simply speak of sperm-cells and spermatoblasts, and distinguish the latter by numbers when they occur in successive generations of different form? Moreover, all the names which have been suggested for successive stages of development, can only be applied to the special group of animals upon which the observations have been made. Hence great confusion results from the use of such terms as spermatoblasts, spermatogonia, spermatomeres, spermatocysts, spermatocytes, spermatogemmae, etc.
[149]. Fol, ‘Sur l’origine des cellules du follicule et de l’ovule chez les Ascidies.’ Compt. rend., 28 mai, 1883.
[150]. Roule, ‘La structure de l’ovaire et la formation des œufs chez les Phallusiadées.’ Ibid., 9 avril, 1883.
[151]. Balbiani, ‘Sur l’origine des cellules du follicule et du noyau vitellin de l’œuf chez les Géophiles.’ Zool. Anzeiger, 1883, Nos. 155, 156.
[152]. Will, ‘Ueber die Entstehung des Dotters und der Epithelzellen bei den Amphibien und Insecten.’ Ibid., 1884, Nos. 167, 168.
[153]. [It is almost certain that this vesicle is not derived from the nucleus, but from the cytoplasm of the sperm-mother-cell. See Douglas H. Campbell, ‘Zur Entwicklungsgeschichte der Spermatozoiden’ in Berichte der deutschen botanischen Gesellschaft, vol. v, 1887, p. 122.—S. S.]
[154]. Bütschli, ‘Gedanken über die morphologische Bedeutung der sogenannten Richtungskörperchen,’ Biolog. Centralblatt, Bd. VI. p. 5, 1884.
[155]. F. M. Balfour, ‘Comparative Embryology,’ vol. i. p. 63.
[156]. The formation of a polar body in parthenogenetic eggs has now been proved: see [note] at the end of this Essay; see also [Essay VI].—A. W., 1888.