As this work treats of parasites only, I purposely refrain from dealing with the Turbellarians, and certain other creatures usually classed with _Vermes_. The vague term “worms,” so often employed as the equivalent of _Helmintha_, is misleading in many ways. I should like to see it adopted only when speaking of the Annelids proper. It would still have a sufficiently wide application, seeing that it would include Leeches, Earth-worms, Naids, Tubed-worms, Sea-lobworms, Sea-mice, Nereids, and a host of other setigerous species. Notwithstanding the remote connection subsisting between “intestinal worms” and worms properly so called, the notion that an intimate relation subsists between the lumbricoid helminths and earth-worms will probably never entirely disappear from the popular or even from the professional mind. Since one of the principal features of this treatise is to afford a handy means of reference to the rich and extended literature of parasitism, I here subjoin a list of general and systematic treatises. To most of these I shall constantly refer. Full special references to detached memoirs will appear in the bibliographies scattered throughout the body of the work. BIBLIOGRAPHY (No. 1).--_Bremser_, ‘Ueber lebende Würmer im lebenden Menschen,’ Vienna, 1819; French edit., by Grundler, 1824.--_Idem_, ‘Icones helminthium,’ Vienna, 1824.--_Cobbold, T. S._, ‘Entozoa, an Introduction to the Study of Helminthology, with reference more particularly to the Parasites of Man,’ London, 1864; Supp., 1869.--Reviews in the ‘Lancet,’ Sept. 24th, 1864, p. 353; in the ‘Med. Times and Gaz.,’ Oct. 29th, 1864, p. 474; in the ‘Athenæum,’ Oct. 15th, 1864, p. 493; in ‘Cosmos,’ Oct. 27th, 1864, p. 463; in the ‘Reader,’ Nov. 26th, 1864, p. 668; in the ‘Edinburgh Vet. Review,’ Nov., 1864, p. 662; in ‘Intellectual Observer,’ vol. vi, 1864, p. 190; in the ‘Quarterly Journal of Science,’ No. v, January, 1865, p. 145; in the ‘Quart. Journ. of Micr. Science,’ New Series, No. 17, Jan., 1865, p. 43; in ‘Popular Science Review,’ Jan., 1865, p. 214; in the ‘Veterinarian,’ Feb., 1865, p. 97; in the ‘Medical Mirror,’ Jan., 1865, p. 23; in the ‘Natural History Review’ for July, 1865; in the ‘British and Foreign Medico-Chirurgical Review,’ April, 1865, in the ‘Edinburgh Medical Journal’ for April, p. 929; in the ‘Social Science Review’ for Feb. 1, 1866, p. 169; in ‘Dublin Quart. Journ. of Medical Science’ for Aug., 1867.--_Davaine, C._, ‘Traité des Entozoaires et des maladies vermineuses de l’homme et des animaux domestiques,’ Paris, 1860, 2nd edit., 1877-79.--_Diesing, C. M._, ‘Systema helminthum,’ Vienna, 1850.--_Dujardin, F._, ‘Histoire naturelle des helminthes ou vers intestineaux,’ Paris, 1845.--_Goeze, T. A. S._, ‘Versuch einer Naturgeschichte der Eingeweidewürmer thierischer Körper,’ Blankenburgh, 1782.--_Küchenmeister, F._, ‘Die in und an dem Körper des lebenden Menschen vorkommenden Parasiten,’ Leipsic, 1855, 2nd. edit., 1878-79; Eng.