| OCR Text |
Show 1894.] NEW GENERA OF EARTHWORMS. 387 terminal chamber of the efferent apparatus in the genus Geoscolex, and it is of course also comparable, as I have already mentioned, to the bursa copulatrix of the Eudrilidae. The walls are thick and muscular and of a spongy texture. At the posterior inner boundary of each sac opens the spermiducal gland. The gland has the tubular character of that of the last species, but it is decidedly more slender; it is, as usual, divisible into two parts-the non-glandular duct, and the glandular portion. The former is of a fair length and slender. It widens out at its actual orifice into the terminal sac. The glandular part of the tube is long and coiled and slender; it is attached to the posterior border of the bursa by a mesentery, which supports it and gives to it somewhat the appearance of a minute vertebrate intestinal tract. The sperm-ducts cross the sac towards the outer border; they are enclosed in a muscular sheath, as is the case with the sperm-ducts of Microdrilus and Pygmceodrilus. The thickness of this muscular coat makes the sperm-ducts hardly, if at all, thinner than the duct of the spermiducal gland. The sperm-ducts pass beneath the terminal sac, so that it is just hidden on a superficial view and opens into it at the posterior outer border, at the opposite " corner," as it were, to that occupied by the orifice of the spermiducal gland. There is, as in the last species, no trace whatever of penial setae. There are but a single pair of spermathecae, which have moved a segment further in front and lie in the viith instead of the viiith segment. They have a remarkable arrangement which I have not seen paralleled elsewhere. The two spermathecae are very close together; in fact they are in actual contact above, but they are separated below by the nerve-cord which runs between them. The area in which the two pouches lie is walled off from the surrounding space by a perfectly circular fold of muscle, which arises posteriorly from the septum, but anteriorly from the ventral parietes. This is really produced by a perforation of the septum to let the spermathecae pass through it. Each spermatheca passes through a foramen, so that it lies in segment vii. to a great extent, but opens on to the exterior between segments viii./ix. The spermatheca itself is the shape of a sock with a very short foot; the toe is directed backwards. The spermatheca is thick-walled but very soft; there is nothing apparent in the shape of a diverticulum. The following is a table of the differences between the species:- Millsonia rubens. Millsonia nigra. Male pores Paired. Unpaired. Spermathecal pores .. VII./VIII. VIII./IX. Stout septa IX./XVH. IV./XIV. Sperm-sacs in X L , XIII. in X L , XII., XIII. Bursa copulatrix Absent. Present. |
