The attachment of the larva by the præ-oral lobe is not more extraordinary than the attachment of a Barnacle by its head, and after such a mode of attachment the atrophy of the supra-oesophageal ganglion would be only natural. There is one important fact which deserves to be noted in the development of the Polyzoa, viz. that if the suggestion in the text as to the mode of development of the adult from the so-called larva is accepted, the Polyzoa exhibit universally _the phenomenon of alternations of generations_. The ovum gives rise to a free form which never becomes sexual, but produces by budding the sexual attached form. BIBLIOGRAPHY. _General._ (298) J. Barrois. _Recherches sur l'embryologie des Bryozoaires._ Lille, 1877. _Entoprocta._ (299) B. Hatschek. "Embryonalentwicklung u. Knospung d. Pedicellina echinata." _Zeitschrift für wiss. Zool._, Bd. XXIX. 1877. (300) M. Salensky. "Etudes sur les Bryozoaires entoproctes." _Ann. Scien. Nat._, 6th Ser. Tom. V. 1877. (301) O. Schmidt. "Die Gattung Loxosoma." _Archiv f. mik. Anat._, Bd. XII. 1876. (302) C. Vogt. "Sur le Loxosome des Phascolosomes." _Archives de Zool. expér. et génér._, Tom. V. 1876. (303) C. Vogt. "Bemerkungen zu Dr Hatschek's Aufsatz üb. Embryonalentwicklung u. Knospung von Pedicellina echinata." _Zeit. f. wiss. Zool._, Bd. XXX. 1878. _Ectoprocta._ (304) G. J. Allman. _Monograph of fresh-water Polyzoa._ Ray Society. (305) G. J. Allman. "On the structure of Cyphonautes." _Quart. J. of Micr. Scie._, Vol. XII. 1872. (306) G. J. Allman. "On the structure and development of the Phylactolæmatous Polyzoa." _Journal of the Linnean Society_, Vol. XIV. No. 77. 1878. (307) J. Barrois. "Le développement d. Bryozoaires Chilostomes." _Comptes rendus_, Sept. 23, 1878. (308) E. Claparède. "Beiträge zur Anatomie u. Entwicklungsgeschichte d. Seebryozoen." _Zeit. für wiss. Zool._, Bd. XXI. 1871. (309) E. Claparède. "Cyphonautes." _Anat. u. Entwick. wirbell. Thiere. Leipzig, 1864. (310) R. E. Grant. "Observations on the structure and nature of Flustræ." _Edinburgh New Philosoph. Journal_, 1827. (311) B. Hatschek. "Embryonalentwicklung u. Knospung d. Pedicellina echinata." (_Description of Cyphonautes_). _Zeit. f. wiss. Zool._, Bd. XXIX. 1877. (312) T. H. Huxley. "Note on the reproductive organs of the Cheilostome Polyzoa." _Quart. Jour. of Micr. Science_, Vol. IV. 1856. (313) L. Joliet. "Contributions à l'histoire naturelle des Bryozoaires des côtes de France." _Archives de Zoologie Expérimentale_, Vol. VI. 1877. (314) E. Metschnikoff. "Ueber d. Metamorphose einiger Seethiere." _Göttingische Nachrichten_, 1869. (315) E. Metschnikoff. _Bull. de l'Acad. de St Pétersbourg_, XV. 1871, p. 507. (316) H. Nitsche. "Beiträge zur Kenntniss d. Bryozoen." _Zeit. f. wiss. Zool._, Bd. XX. 1870.