We have now to consider the eastern region of the world comprising the two regions known generally to zoogeographers as the Oriental and Australian. Taking a large view of the range of sub-families and genera, and endeavouring to make the great regions of the globe more or less equal, it seems difficult to divide further a region which shall include all of this vast territory, and which may therefore be termed Indo-Australian. For we find as characteristic of the entire stretch of country the great majority of the genera of the huge family Megascolecidae. Indeed the largest sub-family of this family, _i.e._ the Megascolecinae, is, save for the mysterious occurrence of the genera _Plutellus_ and _Megascolides_ in America, absolutely limited to this area. Another sub-family, that of the Octochaetinae, is limited to it. So far as concerns the others of the sub-families of Megascolecidae it is only the Trigastrinae which occur here (the genus _Eudichogaster_ and a few possibly introduced species of _Dichogaster_) and a scattered species or two of _Notiodrilus_ of the sub-family Acanthodrilinae. Again there are a few and probably introduced species of the sub-family Ocnerodrilinae. More important still this region has confined to itself the family Moniligastridae; for a species described some years ago by myself from the Bahamas is doubtless an introduced form. We have a complete absence of indigenous Lumbricidae and Geoscolecidae excepting the aquatic _Glyphidrilus_ of the sub-family Microchaetinae. It is true that by taking isolated tracts, even large tracts, of this great regional expanse a sub-division into well characterised regions can be apparently recognised. But in taking such a step we shall be confronted with the curious fact that it is rather neighbouring than widely remote sub-divisions which present the greater differences. If we compare for example India and New Zealand we find in common such striking genera as _Octochaetus_, _Hoplochaetella_ and _Diporochaeta_; whereas these genera are absent from the intervening islands of the great Malay archipelago. On the other hand Australia differs from the comparatively neighbouring islands of Borneo and others by the absence in those islands of the characteristic Australian genera such as _Megascolex_, _Notoscolex_, _Plutellus_ etc. which are in their turn found in India. It is facts like these which render very difficult the apportioning of the tracts of country forming the eastern hemisphere into separate regions. There is no doubt that the Malay archipelago and the adjacent coasts of Asia up to Japan differ from both India and Australia by the almost entire limitation of the genus _Pheretima_ to them; but we cannot intercalate a region in the middle of another geographical area in this fashion!