GLANDS OF AUSTRALIAN EARTHWORMS. 135 
body-wall (fig. 22, a’), but no opening could be seen in relation 
to the central gronp. It is probable, however, that this opens 
by means of a communication with the duct leading from the 
inner of each set of lateral groups. Each group is surrounded 
by a distinct layer containing muscle-fibres. This doubtless 
assists the propulsion of the secretion outwards. Between each 
of the two lateral groups on each side and between them and the 
central group, in the region of the spermiducal-duct opening, is 
a muscular sac (s.s.) containing a large curved but smooth penial 
seta (s‘). There are thus two of these on each side, and the 
gland-groups open, not around the opening of the spermiducal 
duct, but around the penial sete. This will be clear on a reference 
to the figure. 
(2) Glands embedded in the body-wall, e.g. Megascolex dor- 
salis and Digaster excavata. In M. dorsalis (Pl. 15. fig. 23) there 
are two completely different sets of glands separated by the sper- 
midueal duct. The first and upper of these (a.’g.'), which lies to 
the outer side of the spermiducal duct, is composed of a number 
of alveoli. Hach alveolus contains a central cavity surrounded by 
large finely granular gland-cells, each with a nucleus pushed to 
its outer edge. The alveoli are separated from each other by a 
number of connective-tissue septa. No connection could be 
traced between these and the gland-duct, though from their 
position itis probable that they do, at times, open into the spermi- 
ducal duct. The second set are those (a.g.) to be found on the 
inner side of the gland-duct. They are much lower down in the 
papilla. The cells of these groups are much smaller and clearer, 
though arranged as before around a central space. Hach group 
opens on the surface not by means of a single duct, but by a 
number of fine ducts from the gland-cells forming the group. 
These run down and open to the surface between the columnar 
cells of the epidermis. It is the latter set only which are found 
in Digaster excavata. In this form the groups are more nume- 
rous, but more scattered and looser in structure. The groups of 
unicellular ducts, which are longer than in Megascolex dorsalis, 
are to be seen very clearly opening on the surface. One or two 
groups open into the spermiducal duct, close by the opening of 
the sete into the latter. 
