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Show 1893.] GENITALIA OF BRITISH EARTHWORMS. 321 accessory gland are the presence, in the latter, of several multinucleate masses of protoplasm, whose nuclei are smaller than those of the surrounding cells and are arranged around the periphery of this mass of protoplasm (fig. 3 6). These masses closely resemble the mulberry stage in the development of the spermatozoa, as seen in tbe seminal vesicles. Moreover, one observed two masses of darkly staining bodies composed of elongated rods (fig. 3 c), somewhat bent on themselves, which had all the appearance of nearly ripe sperm bundles, although, owing to their being buried up amongst a mass of cells, it was impossible to make out any flagella in relation to them. The general structure of this body and the presence in it of undoubted spermatozoa prove, I think, that it is to be regarded as an over-developed testis, which, having no seminal vesicles (receptacula seminis of Beddard l) into which to discharge its developing spermatozoa, has retained some of them, at auy rate, within its substance until they have become fully developed. The presence of a third testis is interesting as, except for a description of Perrier's 2, no one has, I believe, ever recorded the presence of additional testes in the Oligochaeta 3. With regard to Perrier's case, one cannot doubt for a moment, on referring to his figures, that Vejdovsky 4 is right in saying that " Perrier's testes are in reality the seminal vesicles." If this be the case, then Allolobophora is the first Oligochsete proved to occasionally possess three pairs of testes. This is not the only specimen having this peculiarity, as I have since found two other abnormal forms of A. longa in which additional testes were present on the posterior face of the 11/12 mesentery. Further, when we remember that this testis is developed in exactly the same place as that in which I have described an undoubted ovary in another individual (I. c. plate xiii. fig. 1, ov1), we have further confirmation for the belief that the male and female genital glands in the Oligochaeta, at any rate, are homologous structures and may be developed from the same tissue and in the same situation. Of the left half of the body, longitudinal sections were made so as to pass through the testes, the accessorygland, the ovary, and the segments immediately following (Plate X X I V . fig. 1). On examining the accessory gland in section one immediately noticed, in addition to the general mass of small cells already described, one or two colossal cells (not all visible in the same section), and several moderate-sized ones situated on its dorsal surface (fig. 4). Detailed 1 This term is not altogether a happy one, as the older Helminthologists applied it with perfect justice to the spermathecae. Its application to the seminal vesicles, althougb expressing their undoubted homology with the receptacula ovorum, is apt to cause confusion. 2 "Eecherches p. serv. a l'hist. d. Lumbriciens terrestres," Nouv. Archiv. d. Mus. d'Hist. Nat. Paris, torn, viii., 1872. 3 Bergh, Zeitschr. f. wiss. Zool. Bd. xliv. 1886, p. 308 (footnote), says " abnormally placed additional testes are never found." 4 Syst. d. Oligochaeten, p. 135. |