278 WILLIAM BLAXLAND BENHAM. 
blood-vessels ; and in the spaces between the trabecule are the 
developing spermatozoa. This is the same structure as in 
Lumbricus, but much more compact, and the spermatospheres 
are fewer in number. 
Each sac is united to its fellow of the opposite side, but the 
anterior pair remain quite distinct from the posterior pair. 
We may take the sac in somite x for further examination. 
Each seminal reservoir is constricted as it passes forward 
through the septum into somite 1x into a very narrow neck ; 
in this somite it swells out again into a globular sac, which 
les in the posterior half of the somite ; this contains the ciliated 
rosette of the sperm duct, and so it may be called the “ rosette- 
sac” (r.s.). This latter sac unites across the middle line with 
its fellow of the opposite side, so that the cavity of the two 
seminal reservoirs of somite x are continuous in somite Ix. 
The sacs in somite x1 have the same arrangement. 
6. Testis.—From the rosette-sac, close to the middle line, 
there springs a cylindrical horn-like process (¢. pr.), which runs 
outwards and forwards, and abuts by an obtuse, rounded end 
against the anterior septum of somite 1x; there are two of 
these in somite 1x, one from each of the rosette-sacs. This pro- 
longation is hollow, and its wall consists of a thick layer of 
connective tissue; there springs from a line along its outer 
side a mass of cells with large nuclei, amongst which blood- 
vessels run ; this mass more or less fills the lumen, and is a testis 
(Pl. XVI, figs. 12, 13). The cells are like the sperm mother- 
cells of testis of Lumbricus. This arrangement is repeated for 
the pair of rosette sacs in somite x. Thus there are two 
pairs of seminal reservoirs in somites x, x1; two pairs of rosette- 
sacs in somites 1x, x, and two pairs of the above prolongations 
with enclosed testes in somites Ix, x. The compactness of the 
seminal reservoirs, their more regular shape, and the fewer 
masses of spermatozoa suggest that in this worm the production 
of spermatozoa is not periodical, as in Lumbricus, but more 
continuous, whilst the “testes” are conspicuous, though en- 
veloped in a cecum of the rosette-sac. The testis has the same 
appearance in a section through a mature Lumbricus, as 
