[137]. Weismann, ‘Die Entstehung der Sexualzellen bei den Hydromedusen.’ Jena, 1883.
[138]. [I adopt this term, suggested by E. Ray Lankester and G. C. Bourne, as the name of the supporting lamina of Coelenterata. See ‘Quart. Journ. Microsc. Sci.’ Jan. 1887, p. 28.—E. B. P.]
[139]. Dr. Clemens Hartlaub, ‘Ueber die Entstehung der Sexualzellen bei Obelia.’ Freiburg, Inaugural Dissertation: see also ‘Zeitschrift für wissenschaftliche Zoologie.’ Bd. XLI. 1884.
[140]. English translation, by H. Marshall Ward. Oxford, 1887, Clarendon Press.
[141]. [Such gland-cells are known in both animals and plants. See W. Gardiner and Tokutaro Ito, On the structure of the mucilage-secreting cells of Blechnum occidentale L., and Osmunda regalis L., ‘Annals of Botany,’ vol. i. p. 49.—S. S.]
[142]. Thus in 1877 Bütschli thought that ‘the chief significance of the formation of polar bodies lies in the removal of part of the nucleus of the egg, whether this removal is effected by simple expulsion or by the budding of the egg-cell.’ ‘Entwicklungsgeschichtliche Beiträge;’ Zeitschrift für wissenschaftliche Zoologie, Bd. XXIX. p. 237, footnote.
[143]. C. S. Minot, ‘Account, etc.;’ Proc. Boston Soc. Nat. Hist. vol. xix. p. 165, 1877.
[144]. E. van Beneden and Boveri have recently, quite independently of each other, made a more exact study of these ‘Polkörperchen’ (‘Centrosoma,’ Boveri). They show that nuclear division starts from these bodies, although the mode of origin of the latter is not yet quite clear.—A. W., 1888.
[145]. The existence of polar bodies in sponges has been recently proved by Fiedler: Zool., Anzeiger., Nov. 28, 1887.—A. W., 1888.
[146]. They have now been observed in many species, so that their general occurrence in insects is tolerably certain. Compare bibliography given in Weismann and Ischikawa, ‘Weitere Untersuchungen zum Zahlengesetz der Richtungskörper,’ ‘Zoolog. Jahrbücher,’ vol. iii. 1888, p. 593.—A. W., 1888.