of roundish sacs, with two or three minute diverticula, known as the spermathecae. In the diverticula of these sacs are stored the sperm derived from another individual. [Illustration: Fig. 6. Genital region of _Maoridrilus dissimilis_ (in which species the different organs are essentially as in _Notiodrilus tamajusi_). The oesophagus is cut away between the Xth and XVIIIth segments to display the various organs. _n_ external orifices of nephridia which alternate in different segments; the one lettered opens in front of dorsalmost pair of setae, that of segment XVI opens in front of ventralmost pair, _p_ coiled glands opening on to XVIth and XIXth segments, _sc._ sacs containing long seta, associated with these glands, _t_ spermary of segment; another pair in an exactly similar position in segment XI. Behind spermaries are funnel-shaped openings of sperm ducts which are seen running along the body to their external orifice on XVIIIth segment. _v.s._ sperm sacs behind the posterior of these and in segment XIII is seen the large ovary corresponding in position to the spermary and opposite to each ovary the oviduct. (x 3.)] [Illustration: Fig. 7. A spermatheca of _Notiodrilus tamajusi_. The external orifice is shown at _o_; above this are the diverticula, _s_ is a portion of an intersegmental septum. (After Eisen.)] This completes the general sketch of the structure of _Notiodrilus tamajusi_ which we have selected as a type. In this same genus are a large number of species which differ from that selected in various small structural points. Thus in _N. annectens_ (Beddard), a species from New Zealand, the spermaries and ovaries are attached to the posterior, instead of to the anterior, wall of their segments, and there are neither calciferous glands nor modified setae upon segments XVII and XIX. In all essentials however the two types agree and are thus to be looked upon as referable to the same genus. Starting from the structure of these types we may now sketch in quite a brief way the main divergencies of structure shown in the group of Oligochaeta. We shall naturally begin with the family Megascolecidae of which a type has just been described.