HISTOLOGY OF THE L AND-PL ANARIAN S OF CEYLON. 
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g. Yelk-gland. 
h. Mass of small cells. 
od. Oviduct. 
Fig. 9. Longitudinal section of oviduct of Bipalium Diana in the region of the external 
generative organs. A short lateral branch tube is seen to enter the duct at 
an inclination which slopes towards the posterior extremity of the body. 
The short branch is clothed with cilia, which are directed towards the opening 
into the oviduct. Attached to the extremity of the branch are stroma-fibres 
and fusiform cells, which appear to form branched spaces in the body-substance. 
The branch enters at the external side of the oviduct. The cilia of the ovi- 
duct are seen here, as elsewhere, to be direced towards the termination of the 
duct. The duct has a distinct basement membrane. 
a. Anterior extremity of segment. 
d. Stroma and fusiform cells. 
e. Basement membrane of branch entering oviduct. 
Fig. 10. Transverse section of oviduct of D. Diana , magnified about twice as much as in 
foregoing. The basement membrane is well seen. The cilia appear to have 
a spiral arrangement. 
Fig. 11. Epithelial lining of ovary. 
Fig. 12. Series of stages in the development of ova. The youngest ova cannot be distin- 
guished from the lining cells of the ovary. The germinal vesicle enlarges 
rapidly to its full size ; it then loses its finely granular appearance and becomes 
quite clear and transparent. The investing yelk-mass continues to increase 
in size after the germinal vesicle has ceased growing. The last stage in its 
development is the appearance of large oil-globules in its substance. The 
external capsule, which is seen to invest the more mature ova, is derived from 
the stroma of the ovary. A clear space is seen between the ovum and this 
capsule. 
Fig. 13. Longitudinal section of ovary of Bhynchodemus Thwaitesii in the plane of the 
body. From several preparations. The ovary is seen to be circular in outline. 
The oviduct passes up on the right-hand side of the figure, which corresponds 
to the internal side of the ovary. Where the duct joins the ovary there is a 
mass of fusiform cells, which forms a papillary projection into the : cavity of that 
organ. From this projection stroma-fibres radiate out between the ova. The 
ovary has two investments, as in Bipalium Diana. Immature ova are seen all 
round the margin of the cavity. The mature ova occupy a central position. 
a. Outer loose fibrous investment of ovary. 
1. Inner denser ditto. 
c. Immature ova. 
d. Mature ova. 
e. Stroma. 
