[140] For a discussion as to the structure of the Polyzoon larva, vide Vol. II. p. 305.
[141] Vide Vol. II. pp. 179 and 191. In this connection attention may be called to Cœloplana Metschnikowii, a form described by Kowalevsky, Zoologischer Anzeiger, No. [52], p. 140, as being intermediate between the Ctenophora and the Turbellaria. As already mentioned, there does not appear to me to be sufficient evidence to prove that this form is not merely a creeping Ctenophor.
[142] Quart. Journ. of Micr. Science, Vol. XVII. pp. 422-3.
[143] Vide Hubrecht, “Zur Anat. und Phys. d. Nerven-System. d. Nemertinen,” Kön. Akad. Wiss., Amsterdam; and “Researches on the Nervous System of Nemertines,” Quart. Journ. of Micr. Science, 1880.
[144] Vide F. M. Balfour, “On some points in the Anat. of Peripatus capensis,” Quart. Journ. of Micr. Science, Vol. XIX. 1879.
[145] Vide Vol. II. p. 204.
[146] The independent development of the supraœsophageal ganglion and ventral nerve-cord in Chætopoda (vide Kleinenberg, Development of Lumbricus trapezoides) agrees very satisfactorily with this view.
[147] It is quite possible that Phoronis is in no way related to the other Gephyrea.
[148] This important memoir only came into my hands after this chapter was already in type.