STRUCTURE OF UROCH7ETA AND DICHOGASTER. 257 
and their diameter is considerably less ; their minute structure, 
however, seems to he identical, except that the glandular layer 
is naturally less developed. 
Ovaries. — These organs (fig. 15, o.) occupy the usual posi- 
tion in segment 13 ; they are large and conspicuous. 
Oviducts. — The oviducts (fig. 15, od.) open by a wide, 
funnel-shaped orifice into the interior of segment 13 ; their 
duct perforates the mesentery, dividing this from the succeeding 
segment. Each opens separately on to the exterior ; the external 
orifices are very closely approximated, and lie within the ven- 
tralmost setse at the same level as the apertures of the atria. 
Spermathecae. — There is only a single pair of these organs 
present, which are situated in the eighth segment ; the external 
aperture, as already stated, corresponds in position to the 
ventral pair of setae. The spermatheca is divided into two 
parts (fig. 8), a large sac lying posteriorly and opening on to 
the exterior in common with a mulberry-like structure which 
represents the diverticulum ; as in so many other species of 
Earthworms, the diverticulum lies anterior to the pouch. The 
minute structure of these two sections of the spermatheca 
differs ; the pouch itself is lined (fig. 19) with a tall columnar 
epithelium, which appears to resemble in every particular the 
lining epithelium of the spermatheca of Lumbricus. Outside 
this is a comparatively thin layer of muscular tissue permeated 
by abundant blood-capillaries ; the muscular sheath gets much 
thicker where the pouch narrows to its external opening, and 
here the character of the lining epithelium alters slightly and 
becomes indistinguishable from the epidermis of the body 
surface. The structure of the numerous diverticula differs 
somewhat; the presence of numerous small diverticula gives to 
the region of the spermatheca its mulberry-like aspect. They 
are all, however, enclosed within a common muscular sheath 
(fig. 20), which is proportionately thicker than in the case of the 
spermatheca itself, and abundantly vascular. The diverticula 
are closely packed with bundles of spermatozoa, and the lining 
epithelium differs from that of the spermatheca itself; the 
epithelial cells arc low and cubical. I have called attention 
