OCR Text |
Show ••901.] FROM BRITISH EAST AFRICA. 361 ot which bears a median squarish papilla, which are shown in the figure already referred to. The segments which bear these are xxiv., xxv., xxvi. W h e n the worm is viewed laterally these papilla? are seen to project markedly. Otherwise they are not very conspicuous by reason of colour or texture. As in other species of Gordiodrilus, there is a single calciferous gland in segment ix. There are two pairs of hearts in segments x., xi. The gizzard appears to be entirely absent, as is generally the case in the species of the genus. The septa dividing segments v./x. are thickened, the last septum not to so great an extent as are those which precede it. Male Organs of Generation.-This species of Gordiodrilus, like the majority of its congeners, has two pairs of testes, which occupy the usual segments and the usual position in those segments. They are attached, that is to say, to the anterior septum of segments x., xi. There is nothing noteworthy about the structure of these gonads. The sperm-sacs are rather unusual in number and position. In most of the species of this genus sperm-sacs are present, and it may be that the differences recorded in the number of pairs and the segments which they occupy will prove to be distinctive as marks of specific difference. In Gordiodrilus papillatus there were three pairs of sperm-sacs lying in segments ix., x., xi. These sacs showed the racemose character so often exhibited by these sacs. In addition to the three sperm-sacs, which had thin but perfectly recognizable walls, a mass of loose sperm fills up the ventral part of segments x.. xi., which lodge the funnels of the sperm-ducts. It does not appear that these masses of sperm had any walls of their own, so that they cannot be regarded as sperm-reservoirs ; they are merely, as has been stated, masses of sperm for which presumably no room could be found in the sperm-sacs, as the latter were completely filled with the usual masses of developing spermatozoa. The sperm-ducts commence by large funnels in segments x., xi. They lie, as is always the case, opposite to the corresponding testes. They are much folded, and have not the simple cup-shaped character that sometimes distinguishes the funnels of the lower earthworms. Erom each funnel arises a sperm-duct, and the two ducts of each side are perfectly independent for the greater part of their course. They lie above the muscular layers of the body-wall. A segment or two in front of their opening into the terminal muscular bulbus, to be described immediately, the two ducts of each side unite, so that there is but a single orifice into the muscular bulbus. The glands and other structures associated with the external orifice of the sperm-ducts help by their structure to bridge over the not very wide gap that separates the two African genera Gordiodrilus and Nannodrilus1. The latter genus, originally described 1 " On two new Genera comprising three new Species of_P]arthworms,'' P. Z. S. 1894, p. 388. |