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Show 1892.] SPECIES OF EARTHWORMS. 705 genus is so far degenerated that it possesses no gizzard, not even the faintest vestige of one; the nephridia, which in other Geoscolecidae have a large terminal end sac, very often with a capacious caecum attached, are totally without anything of the kind. Another indication of a low position among the terricolous Oligochaeta is perhaps the opening of the sperm-ducts upon the xviith segment; we find that this segment is the one which bears the pores in question in the genus Ocnerodrilus and also in Microdrilus and Microscolex. It is a coincidence, though probably no more, that there is but one pair of calciferous glands and that these are in the ninth segment; in three low forms of terrestrial Oligochaeta w e meet with exactly the same condition of the calciferous glands, viz., in Ocnerodrilus1, Gordiodrilus 2, and in the Acanthodrilid Kerria.3 As, however, there are Geoscolecids (such as Microchceta) in which the calciferous glands are similarly reduced to one pair, but which are evidently not degenerate forms, too much stress cannot be prudently laid upon the point of similarity to the three genera aforementioned. Rosa4 and 1 5 have independently pointed out that the family Geoscolecidae can be most conveniently divided into two subfamilies, confined respectively (with the exception only of Pontoscolex, which is cosmopolitan) to the Old and to the N e w World; I need not again go into the matter here, as the reasons which led m e to this conclusion have been fully given in the paper quoted below. The present genus interferes with the symmetry of this proposed arrangement ; it evidently belongs in structure to the N e w World section of the family, but lives in the Old World. The spermatothecae lie in front of the testes and the other reproductive organs, and there are no copulatory papillae. The genus Ilyogenia agrees with no other genus in every point: the form and position of the sperm-sacs are unique in the family ; the ventral position of the nephridiopores is characteristic of the genus Geoscolex, with which, however, Ilyogenia has no other marked points of resemblance. It comes nearest, perhaps, to Anteus and Rhinodrilus ; but differs from both of these genera in a number of small differences, which are, in m y opinion, collectively at least, of sufficient importance to justify its distinction by a separate generic name. VII. E X P L A N A T I O N O F P L A T E S XLV. & XLVI. Fig. 1. Part of an egg-sac of Moniligaster bahamensis, showing ripe ova. °' 2. Spermatotheca of Moniligaster bahamensis: a, transverse section. 3*. Ventral view of anterior segments of same; the segments are numbered. 4. Male genital apparatus of the same worm; tbe figure is reconstructed from a series of sections. 1 "On the Anatomy of Ocnerodrilus," Tr. Boy. Soc. Edinb. vol. xxxvi. no. 21. 2 " O n a new Genus of Oligochasta, &c," Ann. & Mag. Nat. Hist., July 1892. 3 P. Z. S. 1892, p. 355. 4 Kynotus michaelsenii, n. sp. " Contribute alia morfologia dei Geoscolecidi," Boll. Mus. Zool. vol. vii. no. 119. 6 Q. J. M. S. vol. xxxiv. p. 258. |