Of the very many genera, however, of which this family is composed, a comparatively small number are thus peregrine in habit at times. All the species known which are distributed broadcast, more or less, over the tropics belong to the genera _Pheretima_, _Microscolex_, _Dichogaster_, _Megascolex_, _Perionyx_, _Ocnerodrilus_, _Kerria_. These several genera are placed in order of frequency of exotic occurrence. Indeed of the two latter genera their frequent life in fresh water may really remove them from the present category altogether. In addition to these are some perhaps more questionable instances, such as the genus _Gordiodrilus_ which, prevalently West African, has also been found in the West Indies, in East Africa, and in India and Madagascar. These instances I propose to leave out of consideration in the present sketch. The most obviously peregrine genus of all those enumerated is _Pheretima_, which according to my experience turns up in almost all gatherings of earthworms from any part of the tropical or even sometimes temperate regions of the world. It seems to be fairly well settled that this extensive genus has its real home in the islands of the Eastern Archipelago, perhaps extending a little in various directions from that centre. But examples of the genus have been found in almost all other regions. And what is especially to the point in considering the facts, as will be pointed out with more emphasis later, the assumedly peregrine species do not differ from those found in the real district in which the genus is indigenous. Dr Cognetti de Martiis enumerates in the Neotropical region, that is in South and Central America and the West Indies, the following species: _Pheretima biserialis_, _P. californica_, _P. capensis_, _P. elongata_, _P. hawayana_, _P. hesperidum_, _P. heterochaeta_, _P. houlleti_, _P. posthuma_, _P. rodericensis_, _P. schmardae_ and _P. violacea._ Of these twelve species it is quite certain that the last six occur in the East, where they are doubtless indigenous. So too do the species _P. biserialis_, _P. capensis_, and _P. hawayana._ The synonymy of the different species of this large genus is not yet in a completely settled condition. But in the meantime it is in my opinion quite possible that both _P. hesperidum_ and _P. californica_ are identical with species also occurring in the East. There remains the somewhat doubtful _P. elongata_ from Peru which has not been very fully described. There is thus no convincing evidence of species really indigenous to and confined to any part of America. Some of these species also occur in many other parts of the world. For instance, _P. heterochaeta_ is very widely spread indeed, occurring as it does in Australia, New Caledonia, Madagascar, and even England (in hothouses). This species indeed is the most prevalent of all Pheretimas and seems to be abundant in gatherings of earthworms from various localities as are _Eudrilus_ and _Pontoscolex_.