No specialized system of spermathecae, sperm reservoirs, and copulatory apparatus, as in Oligochaeta; development generally through a larval form; reproduction by budding also occurs.
Spermathecae nearly always present.
These sacs are dealt with later under the description of the spermathecae, which function they appear to perform.
Associated with these glands are frequently to be found bundles or pairs of long and variously modified setae which are termed penial setae,to distinguish them from other setae sometimes but not always associated with rather similarglandswhich are found anteriorly to these, and often in the immediate neighbourhood of the spermathecae; the latter are spoken of as genital setae.
Spermathecae are generally present in the Oligochaeta and are absent only in comparatively few genera and species.
In a few Enchytraeidae and Lumbriculidae the spermathecae open at the distal extremity into the oesophagus, which is a fact difficult of explanation.
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.
The spermathecae are usually paired structures, one pair to each of the segments where they occur.
In many Geoscolicidae, however, and certain Lumbricidae and Perichaetidae, there are several, even a large number, of pairs of very small spermathecae to each of the segments which contain them.
In the Eudrilidae there are spermathecae of different morphological value.
12 and 13 are shown the spermathecae of the genera Hyperiodrilus and Heliodrilus, which are simple sacs ending blindly as in other earthworms, but of which there is only one median opening in the thirteenth segment or in the eleventh.
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.
There are three pairs of spermathecae situated in segments III-V, a testis in V and an ovary in VI.
Spermathecae often with diverticula.
The intervening segments contain the genitalia, which are on the Oligochaeta plan in that the gonads are independent of their ducts and that there are special spermathecae, one pair.
No separate spermathecae or septal chambers for the development of the ova and sperm.
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.
In the female there is in every fertile segment a pair of spermathecae opening at the nephridiopores.