NERILLA AN ARCHIANNELID. 
411 
epidermal glands are related to the male genital aperture. 
They form a four-cornered area on the ventral surface of 
segments 7 and 8 (fig. 6), and are doubtless to be interpreted 
as specialisations of the ordinary glands found at the base of 
the parapodia in other segments. Composed of a right and 
left set of unicellular glands, their long ducts converge to- 
wards and open into the genital atrium. The swollen bodies 
of these gland-cells are for the most part aggregated in four 
masses at the four corners of the glandular area, and situated 
at the base of the seventh and eighth pairs of parapodia 
(figs. 6, 19). Here they bulge far into the coelomic cavity 
(figs. 23, 25). The granular contents of these cells are 
peculiar, and differ from those of glands in other parts in 
that they acquire a brownish tinge and become highly re- 
fractive in balsam. 
A pair of testes is situated in segment 5 (fig. 19). Each 
testis has a narrow anterior end running forward parallel to, 
and on the inner side of, the neck of the nephridium, until it 
reaches the base of the septum separating the fifth from the 
sixth segment (fig. 21). Here it merges with the coelomic 
epithelium. Behiud the testicular cord enlarges, passes up 
the side of the gut to join the testis of the other side in a 
large median dorsal mass loosely compacted and somewhat 
irregular in shape (figs. 19, 22). The youngest cells are, of 
course, found at the front end of the testis near the septum. 
They multiply and grow backwards, the ripest cells being in 
the dorsal mass, chiefly formed of sperm-morulas, which 
become detached and float off. Finally, fully developed 
spermatozoa abound in segment 5 in mature specimens. 
This fifth segment is shut off in front and behiud by com- 
plete septa, preventing any spermatozoa from straying into 
neighbouring cavities. As the production of spermatozoa 
increases the anterior septum bulges forward as a median 
sac into the fourth segment, and the posterior septum bulges 
backward into segments b and 7 (fig. 19). Ripe spermatozoa 
are carried down the first pair of sperm-ducts to the genital 
pore. We should expect to find testes in segments 6 and 7, 
