356 ALFRED GIBBS BOURNE. 
In a M. sapphirinaoides where the clitellum is well de- 
veloped, the worm, when suddenly killed, makes this region of 
the body very globular by means of certain muscles running 
from the dorsal to the ventral part of the segment on each 
side, and it no doubt assumes this shape when forming the 
ege-capsule, and allows the semi-fluid secretion to set before 
resuming its ordinary shape and crawling out. 
Dorsal pores are never, to my knowledge, present. 
Nephridiopores are usually placed on the very anterior 
margin of the segment in the direction of the outer seta rows, 
but the more dorsal position of the pores of Segments 111—1x, 
and occasionally others, forms a good specific character. It 
serves, for instance, to distinguish between M. grandis and 
M. naduvatamensis, but in the “ ophidioid” group (see 
below) is liable to variation. 
Genital Apertures.—These always lie between the same 
segments, Viz. VII-VIII, X-XI, xI-x11. There is a slight specific 
variation as to their relative distance from the median line, 
but they always lie somewhere between the direction of the 
outer and inner seta rows or precisely in the direction of one 
of those rows. With regard to their character, I can only say 
that in the M. grandis group and in the pellucid group 
papillz commonly protrude from the male pores when killed, 
while in the ophidioid group they do not. 
Body-wall.—This is thickened at the sides in the ophidioid 
group, enabling them to move very rapidly in a serpentine 
manner. 
Septa.—The only septa which thicken are v-v1 to viI-1x, 
and these vary in different species in the extent to which they 
are thickened, the most anterior being in some cases hardly 
any thicker than the majority of septa in the body. The 
peculiar arrangement of some of the septa such as is described 
in M. grandis obtains to a greater or less extent in all 
species. One variation deserves special notice: in some cases, 
asin M. grandis, the arrangement of Septum x-x1 is such as 
to completely shut off the ovaries and oviducts and the aper- 
tures of the ovisacs from the rest of the cavity of the segment ; 
