OCR Text |
Show 704 MR. F. E. BEDDARD ON NEW [PeC. 20, where it passes into the intestine ; the latter tube is ciliated throughout. In the ixth segment a pair of ventrally situated calciferous glands arise from the oesophagus. The lumen of these is much divided; they are very vascular. The circulatory system consists only of two longitudinal trunks-the dorsal and ventral vessels ; I could find neither supra-intestinal nor subnervian. Another pair of longitudinal vessels exist in the anterior region of the body ; these arise one on each side from the free extremity of the calciferous glands, and pass forwards through the septal glands. The last pair of hearts are in segment xi. ; in front of these are two pairs which are equally large. The two pair of testes are in x. and xi.; corresponding to them are two pairs of ciliated rosettes ; the single sperm-duct of each side opens on to the xviith segment, and there are no glands of any kind or penial setaa associated with these orifices. One pair of spermatothecae open on to the anterior boundary of segment ix.; they are simple oval pouches without diverticula and were full of sperm. The sperm-sacs have an arrangement which is unusual among Earthworms in general and hitherto unknown in this particular family; they lie in segments ix. and xii., the intermediate segments being occupied by masses of developing sperm unenclosed by any membrane. The sperm-sacs of segments ix. and xii. are attached to the posterior and anterior septa respectively of their segments respectively and are racemose in form. The ovaries lie in segment xiii. attached, as usual, to the front septum of the segment; they lie just above the nerve-cord, but below the ventral blood-vessel, and in the middle line are squeezed almost flat between the blood-vessel and the nerve-cord. In a continuous series of longitudinal sections the ovary of one side is seen to pass into that of the opposite side without any break, though the middle part is rather thinner. This is one of the very few Oligochaeta with an unpaired ovary ; JEolosoma is another instance, but in that Annelid the ovary is not plainly made up of two fused halves as it is in the species here described. Quite recently Schneider1 has described a Rhinodrilus with a single ovary in segment xvii. : in view of the constancy in the position of the ovary, this statement in m y opinion requires verification. The ripe ova are invariably surrounded by a follicle of relatively considerable thickness ; this follicle has a fibrillated appearance, and there are numerous interspersed nuclei. There were ova, free from the follicle, within the mouth of the oviduct. The oviducts open on to the exterior part in front of the ventral setae. There are no egg-sacs. It is clear that this worm should be referred to the family Geoscolecidae, but it is not clear as to which genus of that family it most nearly approaches : in the first place, it should be noted that Ilyoyenia is in certain respects a somewhat degenerate form when compared with other Geoscolecidae ; this would in any case render the decision as to its affinities a matter of difficulty. The 1 " Ueber eine neue Regenwurm Art auf Trinidad," Dorpat Naturf. Ges. Jhrg. 18, p. 42. |