118 Proceedings of Royal Society of Edinburgh. [sess. 
*5. The clitellum occupies 3-4 segments from the 10th to the 
13th; its epidermis is formed by a single layer of cells, differing 
from the epidermis of the general body surface by their greater 
length and glandular character. 
6. The structure of the longitudinal muscles is more complicated 
than is usually the case with aquatic Oligochseta; the longitudinal 
muscular coat more resembles that of certain Earthworms. 
*7. The nephridia commence in the sexually mature worm in the 
16th segment. 
8. There are two pairs of testes, which are digitate organs attached 
to the anterior septum of segments 10 and 11. 
9. There are two pairs of vasa deferentia opening into the interior 
of these segments by a wide funnel-shaped orifice closely attached to 
the posterior septum. Each vas deferens opens independently on 
to the exterior ; the first pair open to one side of the ventral setee 
on the 11th segment, the second pair open on to the 12th segment 
in front of the ventral pair of setae. 
10. There are two pairs of ovaries , occupying a position corre- 
sponding to that of the testes in the 12th and 13th segments. 
11. There are two pairs of oviducts opening into the interior of 
those segments by a wide funnel closely attached to the posterior 
mesentery ; the external orifices are in the intersegmental grooves 
between segments 12-13, 13-14, on a line with the ventral setae. 
*12. In both vasa deferentia and oviducts the distal section is 
lined with a chitinous membrane continuous with that covering the 
body ; they are in other respects closely similar, and the position of 
the external orifice of the 2nd pair of vasa deferentia is inter- 
mediate between that of the 1st pair of vasa deferentia and of the 
oviducts. 
13. The developing spermatozoa are lodged in sperm sacs, which 
extend from the 9th to the 13th segment, and resemble more closely 
the corresponding structures in many aquatic Oligochseta ( e.g ., 
Tubificidse) than those of Earthworms. 
*14. The ova, which are, when fully mature, of large size (one-half 
the diameter of the body), and loaded with yolk granules, undergo 
their development in egg sacs contained in segments 14-16. The 
ova and egg sacs are more like those of the Tubificidse than those of 
Earthworms. 
