OCR Text |
Show 214 MR. F. E. BEDDARD ON THE OLICOCH^ETE [Mar. 6, it. But they appear to me distinctly to enter the epidermis itself. As in other species, there are two pairs of strongly muscular hearts in segments x. and xi. The spermathecce are very large thin-walled sacs, occupying a large portion of the interior of segment ix. The duct of the spermatheca is very narrow and moderately long. I could find no diverticulum. The testes (two pairs) lie in segments x., xi. opposite to the conspicuous sperm-duct funnels. They are both unenclosed by sperm-sacs. These segments contain masses of developing spermatozoa, which suggest at first sight sperm-sacs. They are, however, unenclosed by any membrane. The sperm-sacs lie in segments ix. and xii., and, as in other worms, are developed from the posterior and anterior walls of those segments respectively. The male efferent apparatus conforms to the type seen in other species of this genus. The male pore, as has already been mentioned, is upon segment xvii. This pore is situated upon a prominent hemispherical papilla, which has not the structure of the adjacent clitellum, but consists of tall non-glandular cells, much taller than the cells of the non-clitellar regions of the integument and between which are no glandular cells. Both of the ventral setae are present, and it is to the outside of these that the actual pore is to be found. There is a common pore for the atrium and the sperm-duct; but the two tubes are confluent only within the thickness of the body-wall. The atria extend back for a considerable distance behind their point of opening, for at least ten segments. The minute structure of the atria needs apparently no description; for they do not seem to differ from those of other species. It must be remarked, however, that the atria are distinctly divisible into the distal glandular region and a proximal thick-walled duct. There is a sharp differentiation between these two regions. The ovaries occupy the usual position in the xiiith segment against the anterior wall of that segment. Opposite to them lie the funnels of the oviducts. The oviducts themselves perforate the body-wall and open to the exterior on the ventral side of the body, as already mentioned. It is noteworthy that an appreciable legion of the oviduct is clearly formed by an invagination from the exterior; for it is distinctly lined with cuticle continuous with the cuticle covering the body. There is no receptaculum ovorum, and this absence I rather presume to be characteristic of this genus and not merely distinctive of this and other species. But although there is no receptaculum ovorum there is an incipient trace of the complicated system of sacs which involve the female reproductive organs in the more highly developed Eudrilidae. This fact is important to note, inasmuch as there are some grounds for looking upon this primitive family or subfamily of Oligochaeta, as Michaelsen regards it (which includes the genera Kerria, Nannodrilue, Ocnerodrilus and some others), as lying at the base |