64 (Tiryniietli Biu-haunu : 



tegumentiiiy plexus of Bourne ; unci one buck as the lateral 

 at first, and then as the sub-intestinal one each side, and ending 

 on the posterior sejDtum of 13. This vessel receives, in segments 

 9, 10, 11 and 12, branches from the alimentary canal which 

 derive their blood from the supra-intestinal, and in segments 

 5, 6, 7 and 8, it gives off branches to the ventral body wall 

 whose origins in some cases are marked by swellings (Fig. 2. 

 Sw.), which probably are contractile, and serve to propel the 

 blood. Bourne (11) has also noted such muscular swellings on 

 his " anterior lateral hearts." 



3.— Dipopochaeta davallia, Spencer. P.R.S. Vict., 1900. 

 Plate XIV., Fig. 3. 



Dissection. — The dorsal vessel is single, sw^ollen in segments 

 13-15, and running forward to the first segment, where it divides 

 into two, and joins the ventral one. At the posterior end of the 

 body the dorsal and ventral are connected by a commissural 

 vessel on each side, and this arrangement is continued forward, 

 in segment 15 there being tw^o such connections in the specimen 

 examined. From the hinder part of segment 13 the dorsal 

 gives off a supra-intestinal running forward to the front of 10, 

 and, in segments 10, 11 and 12 hearts arise from the dorsal 

 running round to the ventral vessel, one pair in the hinder part 

 of each segment. From 9-4 the dorsal gives off a pair of com- 

 missural vessels posteriorly in each segment, and in 4 this beanch 

 gives rise to a lateral which divides into two, one half running 

 forward and one back ; the latter giving in segments 

 4-9 marked branches to the ventral body wall, and uniting 

 in the anterior part of segment 10 wdth its fellow of 

 the opposite side to form a single sub-intestinal vessel which 

 receives branches from the alimentary canal in segments 10-12, 

 deriving their blood from the supra-intestinal, which also gives 

 a vessel on each side to the ventral in segment 13. The branch 

 from the dorsal in segment 3 does not reach the ventral vessel, 

 but the ventral becomes much branched in this region, and is 

 single for the whole length of the body. 



