in VI. There are a
clitellum and sperm ducts which though like nephridia have a larger
funnel and a less complexly wound duct. This family consists of only
one well-known genus, _Aeolosoma_, which contains several species.
They are minute worms with coloured oil drops (green, olive green or
orange) contained in the epidermis. The nervous system is embedded in
the epidermis, and the pairs of ganglia are separated as in _Serpula_,
&c.; each pair has a longish commissure between its two ganglia. The
intersegmental septa are absent save for the division of the first
segment. The large prostomium is ciliated ventrally. The setae are
either entirely capillary or there are in addition some sigmoid setae
even with bifid free extremities. This genus also propagates
asexually, like _Ctenodrilus_, which may possibly belong to the same
family. Asexual reproduction universal.

Group II. _Limicolae._--With a few exceptions the Limicolae are, as
the name denotes, aquatic in habit. They are small to moderate-sized
Oligochaeta, with a smaller number of segments than in the Terricolae.
The alimentary canal is simple and a gizzard or oesophageal
diverticula rarely developed. The vascular system is simple with as a
rule direct communication between dorsal and ventral vessels in each
segment. Nerve cord lies in coelom; brain in first segment or
prostomium in many forms. Clitellum generally only two or three
segments and more anterior in position than in Terricolae. Nephridia
always paired and without plexus of blood capillaries. Spermatheca
rarely with diverticula; sperm ducts as a rule occupying two segments
only, usually opening by means of an atrium. Sperm sacs generally
occupying a good many segments and with simple interior undivided by a
network of trabeculae. Ova large and with much yolk. Asexual
reproduction only in Naids. Egg sacs as large or nearly so as sperm
sacs. Testes and ovaries always free. The following families
constitute the group, viz. _Naididae_, _Enchytraeidae_, _Tubificidae_,
_Lumbriculidae_, _Phreoryctidae_, _Phreodrilidae_, _Alluroididae_, the
latter possibly not referable to this group.

Group III. _Moniligastres._--Moderate-sized to very large Oligochaeta,
terrestrial in habit, with the appearance of Terricolae. Generative
organs anterior in position as in Limicolae. Sperm ducts and atria as
in Limicolae; egg sacs large; body wall thick; va