| OCR Text |
Show 1901.] FROM BRITISH EAST AFRICA. 355 illustrated iu the figure as two oviducts with two funnels, each of which funnels will then correspond to one of the two ovaries. The tube which opens into the sac is clearly continuous at the other end with the oviduct which leads to the exterior. It is as clearly not a diverticulum of the spermathecal sac, so different is the histological structure of the two. The only view that I can take of it is to put it down as a second oviduct which unites with the other, as the two sperm-ducts unite on their way to the exterior ; the inappropriate position of the two funnels, which seems to militate against such a view, m ay be fairly explained by the growth of the enormous spermathecal-sac system. I would further point out that the funnels of the oviducts which open into the receptaculuin ovorum look backward; they are absolutely turned round, and the tube leading to the exterior starts from the front of the funnel and not from behind it, as is normal in Oligochaeta. The same is the case with the presumed funnel of segment xiii., corresponding to the only funnel of segment xiv. The fact that the second (presumed) funnel of segment xiii. looks forward may be perhaps put down to the disappearance of the ovaries and of the receptacula seminis of that side of the body, a fact which has already been referred to. It has retained or reverted to what is presumably the ancestral condition. On the opposite side of tbe body to that which I have just described, there is no receptaculuin ovorum and apparently no ovary; but of this latter fact I cannot be so certain as I am about the former, of which, indeed, there is not the slightest doubt. It became a matter of interest therefore to ascertain what were the conditions of the oviduct. At its orifice into the spermathecal sac above there was no difference whatever. The tube, expanding into what I consider to be a funnel anteriorly, left the sac as a tube iu wliich I did not detect cilia until it arrived at the level of the missing receptaculuin. At this point-where I could not find the least vestige of a receptaculuin-the tube passed without any change of calibre into the ciliated region, which I traced, not absolutely, but very nearly, to the exterior. The two tubes made one continuous tube with the same low columnar epithelium and thick muscular walls, and without any more vestige of a second funnel than there was of a receptaculuin. Both of the two structures have absolutely vanished. W e have thus on the left side of the body a single tube of quite different histological structure to, but leading from, the ccelomic pouch, which constitutes the spermatheca of this w orm, to the exterior. This arrangement of the oviduct is not, however, peculiar to Stuhlmannia. In Lybiodrilus the oviduct divides before the tube ends in its funnels. One branch opens by the usual funnel ioto the receptaculuin, the other into the spermathecal sac. Neither funnel is large, and I could not see any ciliation in either. I find that m y account of Hyperiodrilus and Heliodrilus ' is not quite accurate as regards the relations of the oviducal funnels. 1 " O n the Structure of two new Genera of Earthworms, &c." Quart. Journ. Micr. Sci. xxxii. p. 23.r». |
