^{page no 62 note *} Nova Acta K. Leop.-Carol. Akad., Bd. xlii. (1881), p. 116; tab. v., fig. 21.

^{page no 62 note †} Bull. Sci. France Belg., T. xxx. (1897), p. 156; T. xxxii. (1899), p. 323; Zool. Anz., Bd. xxi. (1898), p. 635.

^{page no 62 note †} Bull. Sci. France Belg., T. xxxii. (1899), p. 313; Mém. Soc. Nation. Sci. Nat. Math. Cherbourg, T. xxxi. (1899), p. 165.

^{page no 62 note §} The expenses incurred during this research have been defrayed by a grant from the Earl of Moray Endowment of the University of Edinburgh.

^{page no 63 note *} In a young post-larval A. ecaudata, 5·5 mm. long, with 46 chætigerous segments, there is no nuchal invagination, but only a faint groove; in an older example, 8·5 mm. long, with 56 chætigerous segments, there is between the prostomium and peristomium a distinct invagination of the epithelium, forming the incipient nuchal organ. Examination of sagittal serial sections of a mature specimen of B. vincenti, 10 mm. long, shows that a nuchal invagination is not present.

^{page no 63 note †} Young examples of A. ecaudata, of about the same size as the specimens of B. vincenti described above, have considerably longer neuropodia.

^{page no 64 note *} Langerhans records examples in which the first gill was borne on the twenty-third and twenty-fourth segments respectively.

^{page no 64 note †} Specimens of adult B. vincenti and of young Arenicola about the same size differ markedly in the amount of their pigmentation. The epidermis of the former usually contains only a few dark granules which are situated chiefly at the anterior end of the worm, but in young examples of Arenicola a considerable amount of yellow or green pigment has already been formed.

^{page no 66 note *} Bull. Sci. France Belg., T. xxx. (1897), p. 158.

^{page no 66 note †} Zool. Anz., Bd. xxx. (1898), p. 636.

^{page no 66 note ‡} Bull. Sci. France Belg., T. xxxii. (1899), p. 291.

^{page no 66 note §} Mém. Soc. Nation. Sci. Nat. Math. Cherbourg, T. xxxi. (1899), p. 166.

^{page no 66 note |} Quart. Journ. Micr. Sci., vol. xliii. (1900), p. 537.

^{page no 66 note ¶} In Arenicola the nephridial apertures are invariably just behind the dorsal ends of the neuropodia.

^{page no 67 note *} The funnels of both nephridia are apparently of a simple type, but they are very difficult to investigate in preserved material, and observations on living specimens are desirable in order to determine more fully the structure of these funnels.

^{page no 67 note †} The wall of the nephridium contains muscle fibres, which are more highly developed in the posterior portion of the organ, especially near the blind end.

^{page no 67 note ‡} Professor Mesnil (Bull. Sci. France Belg., T. xxx. (1897), p. 154), stated that, in his specimens of “Clymenides incertus,” which were undoubtedly young phases of B. vincenti, non-pigmented nephridia were present in the fifth, sixth and seventh chætigerous segments. Apparently the extension backwards of the second nephridium had not attained its full development in these young specimens.

^{page no 68 note *} The writer estimated the number of oöcytes in a mature female Arenicola marina to be about 80,000.

^{page no 68 note †} The lumen of the narrow tube of each nephridium, just behind the funnel, is only about 6μ in diameter.

^{page no 69 note *} An extension of a nephridium through two or more segments occurs occasionally also in the Maldanids, e.g., in Proclymene mulleri, in which the nephridia of the eighth segment extend backwards into the tenth. See Arwidsson, I., Zool. Jahrb. Abt. Syst., Suppl. Bd. ix. (1907), p. 132.Google Scholar But little is known of the nephridia of Maldanidæ.

^{page no 69 note †} A term used by Kollman to designate the abnormal persistence of larval characters in an adult.

^{page no 71 note *} Biol. Bull. Wood's Holl, vol. xiv. (1908), pp. 371–386.

^{page no 71 note †} Namely, L. quadraticeps; Dr Johnson does not appear to have been aware of the case of Branchiomaldane.