Contributions to a Knoiuledge of South African Hirudinea. 251 
in xiv. In xv it has reached the normal level and then passes into the 
crop, which extends along the middle line above the brood pouch. The 
crop gives off six pairs of caeca, which arise either in somites xiv-xix 
inclusive or in xv-xx inclusive. 
The caeca of the crop, like the oesophagus, are very thin- walled, and 
there is some difficulty in tracing the structures of the middle portion of 
the canal. The caeca extend outwards along the sides of the brood pouch 
as far as the meeting-line of dorsal and ventral body surfaces. 
The last pair of crop caeca arise at about the limit of posterior 
extension of the brood sac in the middle line. 
The stomach gives off four pairs of diverticula, as it passes obliquely 
backwards and downwards behind the brood pouch. 
The most marked features of the alimentary canal are the passage of 
the oesophagus through the ovary, and the exceedingly thin nature of the 
wall of the canal between the proboscis and the posterior portion of 
the crop. 
As mentioned in the description of the female organs, the ovary is 
enclosed in a layer of flattened cells which become ellipsoidal at the 
points of entrance and exit of the oesophagus. The oesophageal wall con- 
sists of a single layer of flattened epithelial cells with elongate nuclei. 
This wall is in close apposition with the inner surface of the ovary and 
thus appears as an internal bounding layer. It is thus apparent that the 
ovary has invested the oesophagus. 
Above the oesophagus is the dorsal sinus, which descends and ascends 
with the former in somites xiii and xiv. In xiii, however, it does not 
pierce the ovary, as can be understood, but rests on the dorsal surface of 
the latter, partly invested by the outer layer of cells of the ovary. 
Beproductive Organs. — The male pore is situated between annul 
21 and 22 of the ventral surface, that is between somites xi and xii. 
The female pore occurs between annuli 23 and 24, that is, between the 
second and third annuli of somite xii. 
There are six pairs of testes, situated in somites xiv-xix, a position 
which corresponds with that in other Glossiphoniidae. 
They are greatly drawn out in a dorso-ventral direction and stretch 
along each side of the body in a vertical direction in a crescentic fashion. 
The third and fourth pairs stretch along the outer sides of the brood 
pouch. 
Masses of mature spermatozoa occur in sinuses in the dorsal portion 
of the brood pouch region of the body, and ventrally anterior and posterior 
to the pouch.. 
The male ducts are interesting in that the vas deferens communicates 
anteriorly with a loop which communicates with the vesicula seminalis. 
The formation of this loop is undoubtedly brought about by the displace- 
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