| OCR Text |
Show 32 MR. F. E. BEDDARD ON EARTHWORMS [Jan. 5, beyond the atrium, and, I imagine, open just at the atriopore, as in Ocnerodrilas ; but I am not certain about this. The atriopore is situated just to the outside of the ventralmost seta, which is not modified in any way; there are, in fact, no penial setae, such as occur in the other two species of the genus. The ovaries are in segment xiii. The oviducts open by funnels into this segment opposite to the ovaries, and open to the exterior on segment xiv. Receptacula ovorum are present, and are of considerable size relatively to the sperm-sacs. There is a single pair of spermatothecae present in segment ix.; each opens on to the exterior just behind the septum which separates this segment from the one in front and in a line with the ventral seta. Each spermatotheca consists of an oval pouch and a single narrow diverticulum opening into it in front. MICROSCOLEX POULTONI, n. sp. It may be permissible to append to this paper the description of a fourth species of Microscolex, of which a number of examples were kindly collected for me in Madeira by Mr. E. B. Poulton, F.R.S. They measure, when preserved, about an inch in length ; they are of a brown colour, the clitellum being orange. The clitellum is variable in extent, always, however, including segments xiv.-xvi.; in some specimens a part or the whole of segments xiii. and xvii. belonged also to the clitellum. Segments xiv.- xvi. were much broader than those immediately adjoining. The seta are disposed as in other species of the genus ; but upon the clitellum the ventral pair of setse of each side get very much closer together. On segments xiv., xv., xvi., and xviii. the ventral setae (see drawing, fig. 1, p. 33) are separated from each other by a distance which is less than half that which separates the corresponding setae of segment x. From segment xix. backwards, and from segment xiii. forwards, the distance between the two ventral setae of each side gradually increases. The male pores are upon segment xvii.; each is situated upon an oval elevation, and through the aperture itself protrudes a single penial seta, which corresponds in position to the innermost seta of the ventral pair. The penial setae of this Microscolex are (see fig. 2, p. 34) long, slightly curved, and not ornamented at the free extremity ; when examined under a high power they show a faint transverse striation which marks the successive deposits of chitinous matter in the formation of the seta. There is a slight notch some little way in front of the distal extremity. The pharynx occupies the first 5 segments or so; there is not a great development of glands upon its upper surface, and there is no continuation of these septal glands into the oesophageal segments, such as occurs in Microscolex algeriensis. The oesophagus immediately following the pharynx has, perhaps, slightly thicker walls than the hinder part; but there is nothing that can be fairly termed a gizzard. |
