OLIGOCHATA OF TROPICAL EASTERN AFRICA. 239 
the median sac, that occur in the remaining species, are here 
quite absent; the storage of the sperm is effected by a de- 
velopment, not met with in the other species, of the anterior 
end of the sac on each side. 
I investigated the structure of the female reproductive 
organs in an immature example of this species. The sper- 
matothecal sac was almost filled by small rounded cells, 
quite unlike the tall columnar cells which line the mature 
spermatothecal sac of Polytoreutus violaceus. So nume- 
rous were these cells that the lumen of the entire tube was 
almost completely obliterated. I had hoped to find some 
indication of the position of the ovary in this specimen; but, 
unless the epithelium lining the two end pouches into which 
the spermatothecal sac divides anteriorly is the germinal 
epithelium, I could find nothing at all. There is not, as there 
is in P. violaceus, a small sac attached to the main sperma- 
tothecal sac, set apart for the lodgment of the ovary. It is 
probable that the ovary is only free in very young specimens, 
and it is also possible that it has a very transitory existence. 
There is a precedent for this in Libyodrilus. In that genus 
the ovary appears to exist only for a short time, its contents 
being early transferred to the interior of the egg-sacs. In this 
young specimen of Polytoreutus kilindinensis the egg- 
sacs were quite fully developed as regards size, but they 
contained only quite immature cells ; the germinal cells filling 
the egg-sacs were exactly like the cells in the immature ovary 
of other worms; it is evident, therefore, that the germinal 
tissue is transferred en masse to the egg-sac, and that the 
entire development of the ova goes on in those sacs. The 
spermatothecal sac seems not to be formed by an invagination 
from the epidermis; the epithelium lining it bears no resem- 
blance at all to the epidermis; the structure of the sac is 
exactly like that of the developing sperm-sac which lies in the 
preceding segment; in the section of the worm the two could 
be very well compared, as they almost came into contact. 
Judging from structure only, no one would hesitate to regard 
the two structures as of the same nature. 
VoL. 36, PART 2.—NEW SER. R 
