[248] H. Fol, “Etudes sur le dével. d. Mollusques.” Mem. III. Archiv d. Zool. expér. et génér., Vol. VIII.
[249] The careful observations of Fol seem to me nearly conclusive in favour of this limb having an external opening, and the statement to the reverse effect on p. 280 of Vol. II. of this treatise, made on the authority of Rabl and Bütschli, must probably be corrected.
[250] “On the Structure of the Nephridia of the Medicinal Leech.” Quart. J. of Micr. Science, Vol. XX. 1880.
[251] Vide F. M. Balfour, “On some points in the Anatomy of Peripatus Capensis.” Quart. J. of Micr. Science, Vol. XIX. 1879.
[252] In my original account of the development I held these tubes to be invaginations of the peritoneal epithelium. Sedgwick (No. [549]) was led to doubt the accuracy of my original statement from his investigations on the chick; and from a re-examination of my specimens he arrived at the results stated above, and which I am now myself inclined to adopt.
[253] Five or six segmental tubes belong to the region of the undivided anterior part of the segmental duct, which forms the front end of the Müllerian duct; but they appear to atrophy very early, without acquiring a definite attachment to the segmental duct.
[254] Acipenser has been investigated by Fürbringer, Salensky, Sedgwick, and also by myself, and Lepidosteus by W. N. Parker and myself.
[255] I have not fully proved this point, but have never found more than one opening.
[256] Whether the segmental tubes are formed as ingrowths of the peritoneal epithelium, or in situ, could not be determined.
[257] Dansky and Kostenitsch (No. [543]) describe the Wolffian duct in the Chick as developing from a groove opening to the peritoneal cavity, which subsequently becomes constricted into a duct. I have never met with specimens such as those figured by these authors.