STRUCTURE OP UROCH^TA AND DICHOGASTER. 247 
to lie opposite to the setae of segments which in reality are con- 
siderably behind those which contain the several organs. In 
correspondence with the arrangement of the septa the oviducts 
run forward for some distance before opening on to the 
exterior. Their position, however, is in reality perfectly 
normal. The external apertures are upon the fourteenth 
segments, and the funnels open into the thirteenth. 
The vasa deferentia funnels open into the segment in front, 
i. e. the twelfth. 
In two specimens I found the female reproductive apparatus 
fully developed, and the male organs, with the exception of 
the vasa deferentia, not fully developed. The vesiculae semi- 
nales in those individuals were very readily visible as out- 
growths of the posterior side of the septum which separates seg- 
ments 13 and 14 ; the vesicula was in the condition illustrated by 
Bergh (11) in Lumbricus on pi. xxi, fig. 13, of his memoir. It 
consisted for the most part of a solid mass of cells, with a narrow 
lumen extending for a very short way into its thickness. 
In these specimens (PI. XXIII, fig. 2) there were no testes, 
but the twelfth segment as well as the thirteenth con- 
tained a pair of ovaries. In another individual the gland 
of the thirteenth segment contained ova in abundance. There 
were also a few ova in the gland of the twelfth segment. I 
figure (PI. XXIII, figs. 3, 4) a small fragment of the glands of 
segments 12 and 13. In another specimen in which the vesiculae 
seminales were in a further advanced condition, the genital 
gland of the twelfth segment and that of the thirteenth segment 
appeared to be a testis. These facts are, of course, a confir- 
mation (though indeed a confirmation is hardly wanted) of the 
accepted view that the ovaries and testes are serially homo- 
logous structures. Prom this point of view the facts are of just 
as great importance, even if it were shown that the individuals 
were only abnormal. I am inclined to believe, however, that 
they are not so, and that in Urochseta the same gland 
may produce ova or spermatozoa. 
In all the four individuals which I investigated by means of 
longitudinal sections there were a number of bodies resembling 
