42 Mr. H. A. Bay lis on a new 



limit of the medullary parencliyme, and more towards the 

 middle line of the segments than the lateral nerves; their 

 distance from the nerves is about equal to the distance of the 

 latter from the edges of the segments. The vessels follow a 

 slightly undulating, almost straight course in the mounted 

 specimens which I have examined. 



The ventral longitudinal vessels are not present as a 

 distinct pair of canals, but are represented by a complicated 

 system of intercommunicating tubes, of small diameter, 

 ramifying throughout the medullary parencliyme from side 

 to side. This system (PI. VI. fig. 3) may be said to consist 

 essentially of four main longitudinal vessels, connected at 

 the junction of each segment with its neighbour by a trans- 

 verse vessel. The tubes are swollen into " nodes " at each of 

 the points where they cross each other. Here and there 

 irregular anastomoses between the vessels occur, a vessel 

 sometimes forking and meeting one of the transverse con- 

 necting vessels at two points instead of one. 



Genital Organs. — The female organs are the first to appear 

 in the young segments. Rudiments of them are seen very 

 far forward in the neck of the worm, at about 1'2 mm. from 

 the anterior extremity, and before the boundaries of the 

 segments are well marked. The male organs do not make 

 their appearance for some distance behind this point. 



The female glands (fig. 2, Ov.) are situated in a compact 

 group somewhat to the left or pore side of the segments. 



The testes (fig. 2, T.) are numerous, and two unequal 

 groups of them can be distinguished, though they form an 

 almost continuous series across the segment. One group, the 

 smaller of the two, lies between the lateral limit of the 

 medullary parencliyme on the left side and the female 

 glands. The larger group extends from the right-hand limit 

 of the medulla, in a somewhat wedge-shaped form, nearly as 

 far as the female glands. The testes in this group are more 

 numerous and more closely crowded towards the edge of the 

 segment than towards the middle. On either side of the 

 segment the testes extend beyond the dorsal excretory vessel. 

 They have an average diameter of 0*0375 mm. 



The cirrus-^ac (rig. 2, C.S.) is small and thin-walled. 

 It measures O'l mm. in length and 0'06 mm. in width at the 

 widest part, which is near the inner end. The cirrus appears 

 to be unarmed. 



The genital ducts pass ventrally to the dorsal excretory 

 vessel and dorsally to the nerve. 



The vas deferens is not thrown into any large coils, but 

 runs a comparatively straight course, with small undulations, 



