MONILIGASTER GRANDIS, A. G. B. 311 
Clitellum.—A clitellum undoubtedly develops—at a cer- 
tain restricted time of year—in connection with Segments x, 
XI, x11, and x111. It commences, even in the most fully de- 
veloped specimens which I have seen, on the second annulus 
of Segment x. It is not developed at all upon the ventral area 
of Segments x, x1, and x11, and so does not actually include 
either the male or the oviducal pores, but it is developed over 
the whole of Segment x111._ Before it becomes recognisable in 
living specimens, it may be distinguished in a worm which 
has been placed in spirit for half an hour, as the future clitellar 
area then becomes orange-coloured. 
Mouth.—The mouth is ordinarily completely occluded by 
the retracted prostomium, but it is capable of great distension. 
From time to time the worm protrudes the prostomium and 
the whole of the buccal membrane, and, indeed, the whole of 
the dorsal wall of the pharynx. 
Anus.—The anus is a narrow vertical slit. 
Dorsal pores.—There are no dorsal pores. 
Nephridiopores.—These are very easily seen. There is a 
pair in every segment, except Segments 1 and 11 and the two 
most posterior segments. They are all placed close to the in- 
tersegmental groove, but upon the auterior portion of the 
segment in which the nephridium les. The seven most 
anterior pairs of nephridiopores, 1. e. those of the nephridia of 
Segments 111—1x, lie to an equal extent dorsad of the outer 
seta row. The remaining pores lie exactly in the outer seta 
row.! 
Genital Apertures.—There are three pairs of genital 
apertures, all strictly intersegmental, and lying between Seg- 
ments VII-VIII, X-XI, and x1-x11 respectively. 
The male pores lie between Segments x-x1i, and slightly 
dorsad of the inner seta couple. They are large oval apertures, 
and the immediately adjacent annuli form concentric lips (fig. 
15), and the surface is here and in the immediate neighbour- 
1 This peculiar arrangement shows how careful it is necessary to be in de- 
scribing the position of nephridiopores, especially in spirit specimens, where 
it is often very difficult to see them at all, 
