SOME LITTORAL OLIGOCHATA OF THE CLYDE. 37 
anterior part of iv. ; the second begins above, near the junction of ili. and iv., and ends 
below, just behind the first; the third is wholly contained in segment iv., the fourth in 
v. The last two join the ventral vessel below, the first two join the branches which 
unite to form the ventral vessel. 
The celomic corpuscles are round or broadly oval, disc-shaped, and granular ; they 
are of large size, measuring in the fresh state from 22 to 36 mw; as seen in sections, 
however, they are smaller, and average 20 mu, the largest measured being 25 u. They 
are not obviously nucleated in the fresh condition ; the nucleus is conspicuous in stained 
preparations, lying in the middle of a loose reticulum. They are very numerous, and 
the body-cavity may be crowded with them. 
The nephridia begin in segment v., but are absent in xi. and xiii. The ante-septal 
portion consists of the funnel only ; the post-septal is a large ovoid mass, coloured by a 
/ 
\ 
Fic. 3.—Cerebral ganglion of Marionina semifusca. 
brown pigment in its anterior half; the tube is loosely coiled within the mass of the 
organ. The external openings are in this species easily visible when a specimen is 
examined from the ventral surface ; they are in front of the ventral sete. According 
to the evidence of sections, the duct comes off from the mass of the gland well in front 
of the middle, though this was not made out in the living specimens ; but both modes 
of examination show that it runs backwards to the external aperture, not forwards, as 
figured by CLapaREDE for his specimens. 
The cerebral ganglion is one-and-a-half times as long as broad; anteriorly the 
margin is straight, posteriorly the ganglion is deeply indented (fig. 3). The ganglia 
on the ventral nerve-cord are conspicuous, especially in the anterior part of the body. 
“ Copulatory glands” occur in the neighbourhood of the genital segments (cf SourHERN). 
The testes are large, equal in length to the anterior half of segment x1.; they are 
somewhat triangular in shape, attached by their narrow end, with the base of the 
triangle directed posteriorly. The funnel is short, ovoid, one-and-a-half times as long as 
broad, with an obvious lumen in which ciliary action is very visible ; in general structure it 
resembles related forms. The sperm morulx appear to be confined within the limits of | 
seoment xi., septum 1} being slightly bulged backwards. The vas deferens is thin, 
