In many earthworms there are, at the external opening of the male ducts, bundles of specially modified chaetae, which have been called, from their supposed function, penial chaetae; they are usually ornamented at the free end with spinelets or ridges, and frequently offer valuable specific characters. In the Lumbricidae and the Geoscolicidae there are modified chaetae upon the {363}clitellum; in a few forms, such as, for example, _Acanthodrilus schmardae_, the spermathecae have bundles of similar chaetae in their neighbourhood, often associated with glands not unlike the spermiducal glands. In most, perhaps in all Oligochaeta the sperm is not matured in the testes, or even in the body-cavity; it is received into special sacs which are called sperm-sacs, and there ripens. These sacs, the vesiculae seminales, have been shown to be outgrowths of the septa; their cavity is thus a portion of the body-cavity shut off more or less completely from the general body-cavity. The reproductive organs of the Eudrilidae, and particularly the female organs, are so divergent in many particulars from those of other Oligochaeta that it is convenient to treat them separately. The testes are normal, save that they are often adherent to the posterior wall of their segment, as, however, is the case with some other earthworms. In many Eudrilidae, for instance in the genus _Hyperiodrilus_, the funnels of the sperm-ducts are dependent from the anterior wall of the segment which contains them; the narrow tube which follows projects into the segment in front, and is there immediately dilated into a wide chamber, which again narrows, and bending round, re-traverses the same septum; the two ducts of each side (if there are two, which is not invariably the case) remain separate and open separately into the glandular part of the spermiducal gland. There is occasionally only a single median gland; and as a general rule the two glands open by a median unpaired orifice. Penial chaetae may or may not be present. [Illustration: FIG. 193.—Female reproductive organs of _Hyperiodrilus_. XII-XV, Segments of the body; 1, spermathecal sac; 2, egg-sac; 3, spermatheca; 4, ovary.]