Frank Beddard - Earthworms and Their Allies

Several genera, Pristina , Nais , Dero , are found in many parts of the world; but it is not possible at present to consider very seriously the facts of their geographical distribution.

Next to the Naids a group of aquatic worms present themselves for consideration which are usually placed in three distinct families, which families are however rather hard to define. These three families are the Tubificidae , Phreodrilidae , and Lumbriculidae . The Phreodrilidae were at one time placed with the Tubificidae by Michaelsen. It is now perhaps the general opinion that they form a family of their own, at any rate since the discovery of two other genera Phreodriloides and Astacopsidrilus , besides the original genus founded by myself, and named Phreodrilus from the fact that the species was found in a deep well in New Zealand.

The distribution of this family especially of the genus Phreodrilus is extremely interesting. The genus Phreodrilus is the only one genus of the aquatic Oligochaeta which has, like Notiodrilus , a circumpolar range, the pole being the south pole. It occurs in New Zealand, in Kerguelen, and, if we are to accept the opinions of Drs Michaelsen and Benham that my genus Hesperodrilus is to be merged in Phreodrilus , in Patagonia also.

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 1 With many synonyms, including Tubifex ater (see p. 53). ' 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.

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

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With many synonyms, including Tubifex ater (see p. 53).