A case, even more striking than that of _Pontoscolex_, is afforded by the Eudrilid genus _Eudrilus_. As with _Pontoscolex_ there are two species of this genus, one, _E. pallidus_, being confined to West Africa, the remaining one, _E. eugeniae_, being world-wide in range. This latter species has received the following names, viz. _E. decipiens_, _E. lacazii_, _E. peregrinus_, _E. sylvicola_, _E. boyeri_, _E. jullieni_, _E. erudiens_, and _E. roseus_; they appear to be all synonyms of the name originally given by Kinberg who however did not recognise the distinctness of the form as a genus. It is now known as _Eudrilus eugeniae_. The variety of names given to supposed different forms (for two of which I am myself responsible) is due to the fact that in earlier days when nothing was known about the geographical distribution of this group of animals it was thought by no means unreasonable that a given genus represented by several species should range over the globe. This fact coupled with imperfect description of structural details led to the multiplication of supposed species, a position which is no longer tenable. This worm is quite as abundant in gatherings from all parts of the world as is _Pontoscolex corethrurus_; and in addition to the countries inhabited by the latter, _Eudrilus eugeniae_ has been met with in New Caledonia: tropical Africa is probably its original home. The two families that have been hitherto considered offer no further instances, among their many species, of worms with so wide a range as those just dealt with. There are indeed one or two forms, _e.g._ _Criodrilus_ and _Glyphidrilus_, which have a considerable range though not nearly equalling that of _Eudrilus_ and _Pontoscolex_. These are, however, aquatic forms and the range of aquatic forms is determined as far as we can see by a different series of causes to that of terrestrial forms, which are referred to later. Among the Moniligastridae we have apparently an instance of a peregrine form. The genus itself has its headquarters in Ceylon and extends a little way in other eastern regions; there is, however, one species, _Moniligaster bahamenis_, described some years since from the Bahamas which must surely be an example of a peregrine form, particularly since it is probably identical with _M. japonicus_ whose name is indicative of its habitat. Among the huge family of the Megascolecidae there are a considerable number of species which apparently possess the same facilities for making their way in different directions and across seas from the locality that is thought to be their real home.