In a few Enchytraeidae and Lumbriculidae the spermathecae open at the distal extremity into the oesophagus, which is a fact difficult of explanation.
In the Eudrilidae there are spermathecae of different morphological value.
No separate spermathecae or septal chambers for the development of the ova and sperm.
Among the aquatic Oligochaeta and many earthworms (the families Lumbricidae, Geoscolicidae and a few other genera) the spermathecae are simple structures, as has been described.
It is a remarkable fact, not yet understood, that in certain Enchytraeidae and Lumbriculidae the spermathecae open into the oesophagus as well as on to the exterior.
The large sacs which have been termed vagina are suggestive of the large coelomic spermathecae in Eudrilids, a comparison which needs, however, embryological data, not at present forthcoming, for its justification.
There are three pairs of spermathecae situated in segments III-V, a testis in V and an ovary in VI.