50.--_Leuckart_, l. c., Bd. ii, s. 258.--_Meissner, G._, “Beobachtungen über das Eindringen der Samenelemente in den Dotter,” S. and K. ‘Zeitsch.,’ 1854, s. 208.--_Morton, T._, “Another Example of the Occurrence of _A. mystax_, from a Child of fourteen months old,” in a letter to the ‘Lancet,’ March 11th, 1865, p. 278.--_Nelson, H._, “On the Reproduction of _Ascaris mystax_,” ‘Proc. of the Royal Soc.,’ in ‘Philosoph. Trans.,’ and in ‘Med.-Chir. Rev.,’ 1051-52; also in ‘Froriep’s Tagsbericht.,’ 1852, s. 205-207.--_Rudolphi_, ‘Synops.,’ p. 42, 1819.--_Schneider_, “Ueber Bewegung an dem Samenkörperchen der Nematoden,” in ‘Monatsb. d. Berliner Akad.,’ 1856, s. 192.--_Idem_, ‘Monographie der Nematoden,’ Erste Abth., s. 38, und Dritte Abth., s. 263 (“Entwicklungsgeschichte”), 1866.--_Siebold_, ‘Vergleichende Anatomie,’ 1848, s. 153, and in Burnett’s edit., p. 125 _et seq._, 1854.--_Thomson, A._, art. “Ovum,” in ‘Todd’s Cyclop. of Anat. and Phys.,’ supp., 1859.--_Idem_, “Ueber die Samenkörperchen, die Eier und die Befruchtung der _Ascaris mystax_,” S. and K. ‘Zeitsch.,’ 1856, s. 425.--_Idem_, “Report of Glasgow Meeting” (‘Brit. Assoc. Rep.’), 1855, p. 158. _Ascaris maritima_, Leuckart.--This is a well-marked species. Judging from the characters presented by the solitary, sexually-immature female which supplied Leuckart with his only means of diagnosis, this worm may be briefly described as a filariform nematode about 3/4″ in length and about 1/25″ in breadth. Although there are no cephalic aliform membranes, the cuticle immediately below the lips forms small and distinct projections, one on either side of the head (‘Die Mensch. Par.,’ Bd. ii, s. 877). This entozoon was discovered by Dr Pfaff at Jacobshavn, near Godhavn, West Greenland, in April, 1865. Two years later he sent the specimen to Krabbe, who afterwards transmitted it to Leuckart. In the original communication addressed to the Copenhagen helminthologist, Dr Pfaff states that he procured the worm from amongst matters vomited by a child, and he incidentally observes that he had hitherto encountered only _Bothriocephalus cordatus_ and _Oxyuris vermicularis_ amongst Greenlanders. As to the source of infection, Prof. Leuckart not unnaturally refers to the similar conditions of existence shared by the human and carnivorous inhabitants of that country. It is well known that bears, polar-bears, seals, and walruses are largely infested by nematodes (_Asc. transfuga_, _A. osculata_, _Ophiostoma dispar_, &c.), but these various species are quite distinct from Dr Pfaff’s little “spulwurm.”