134 MISS G. SWEET ON THE SPERMIDUCAL 
what might have been expected from the external form, for it is 
often difficult to know to which group to refer the glands in 
these species by merely examining the outside of the gland. 
Il. Accessory Glands. 
(1) Glands found within the cceelom, as in Megascolides inter- 
medius, M. attenuatus, and Diplotrema fragilis. These include 
two distinct types. In Megascolides intermedius and M. attenu- 
atus the glandular masses occupy the internal surface of the 
ventral body-wall between the spermiducal ducts. In the former, 
M. intermedius (Pi. 14. fig. 3), these structures (a.g.) vary in the 
number of segments they occupy, e. g. from two to four segments, 
or they may even be absent altogether. In IL. attenuatus they 
were found to occupy three segments—17, 18,19. They consist 
(Pl. 15. fig. 21) of a mass of long unicellular glands covered by 
the thin peritoneal membrane ; the gland-cells have pear-shaped 
outer ends, with granular contents and distinct nuclei. The long 
narrow duct-like inner ends of these cells (g."¢.") run down 
through the longitudinal and circular layers, and open on the 
ventral surface between the columnar cells of the epidermis. In 
MM. attenuatus the gland-cells at the sides of the mass are much 
(sometimes two or three times) longer than those in the centre, 
otherwise they resemble those in M. intermedius. In each case 
the nerve-cord runs above, and is supported by the glandular 
mass. In M. intermedius (fig. 3) the surface is seen to be 
mottled, owing to the presence of small patches of brown pigment. 
Diplotrema fragilis (P1.15. fig. 22).—Here the gland-mass takes 
up the ventral surface of segments 16 to 20 or 21. It is divided 
up transversely by the septa which traverse it. In segment 18 
the spermiducal duct runs down alongside this accessory gland- 
mass to open on the surface. In microscopic structure the 
gland-mass is very different from that in Megascolides inter- 
medius. It is composed of a number of groups, a central one on 
which rests the nerve-cord, and two others on either side of this 
(cf. fig.). Hach contains a central cavity which is lined by 
w single row of very granular cells varying somewhat in size, 
each with a nucleus. The cavity of the central group is some- 
what irregular, while its floor is formed by the layer of longi- 
tudinal muscles on which are situated gland-cells. Hach of the 
lateral groups has a definite opening to the exterior through the 
