In this genus the male pores are upon the XIIth segment while the spermaries lie in segment XI. Moreover the spermathecae lie behind the male pores. In the Tubificidae on the other hand it is at least the rule for the spermaries and male pores to be pushed a segment further forwards. And the spermathecae are before the male pores. _Phreodriloides_ is like _Phreodrilus_ but has no spermathecae. It is also New Zealand in range. _Astacopsidrilus_ is Australian and is semi-parasitic upon the Crayfish _Astacopsis_, whence its generic name. _Phreodrilus branchiatus_ is one of the few forms of Oligochaeta that possesses gills. Of these there are a series of pairs on about the last eleven segments of the body. They are lateral in position, and thus contrast with the also gilled _Branchiura sowerbii_, where the gills, also on the posterior segments of the body, are more numerous and lie dorsally and ventrally, a pair to each segment. The Tubificidae differ from the Phreodrilidae mainly in the points already noted. There are a considerable number of genera of which the following are the best known, viz., _Tubifex_, _Limnodrilus_, _Limnodriloides_, _Branchiura_, _Lophochaeta_, _Ilyodrilus_, _Psammoryctes_, _Clitellio_, _Telmatodrilus_, _Bothrioneuron_, _Lycodrilus_. The Tubificidae are mainly northern temperate forms, and a few of them such as _Clitellio arenarius_ and '_Peloryctes inquilina_[1]' are found on the sea coast. There are also a few of this family in the southern hemisphere. These forms include _Clitellio abjornseni_ from Australia, and a few species of _Branchiura_ from New Zealand and the islands of the Antarctic ocean. There is also to be mentioned _Rhizodrilus_ (or _Vermiculus_) _aucklandicus_ from the island of that name in the New Zealand area. The only tropical species appears to be the Indian and Malayan _Bothrioneuron iris_, though this genus also occurs in Europe and in southern South America. It is quite likely however that _Branchiura sowerbii_, a species known at present from tanks in hot houses, may be a tropical American species. [1] With many synonyms, including _Tubifex ater_ (see p. 53). The family Lumbriculidae is yet more restricted in its range. It has not yet been met with away from the temperate northern hemisphere, and the great variety of species recently described from Lake Baikal by Dr Michaelsen is a very remarkable fact. The Lumbriculidae are entirely fresh water in habit and not even partially terrestrial. The following are the principal known genera: _Lumbriculus_, _Trichodrilus_, _Rhynchelmis_, _Phreatothrix_, _Claparedilla_, _Stylodrilus_, _Mesoporodrilus_, _Sutroa_, _Eclipidrilus_, _Aurantina_, _Athecospermia_, _Lamprodrilus_, _Teleutoscolex_.