Australian Eartliworms. 63 



opening a branch to the sub-intestinal vessel (Fig. 20). From 

 the alimentary canal a vessel passes on each side uniting in 

 the middle line (Fig. 20, M. V.), and then passing to the sub-intes- 

 tinal as a single vessel on each side. Close to this opens 

 a branch from the ventral body wall and nephridia (Fig. 20 

 Ef. Ne). Since that to the excretory organs is given off from 

 the heart just before the latter joins the ventral vessel, the 

 blood is propelled to them with the full force of the contraction 

 of the heart. This agrees with Bourne's (11) description of the 

 course of the blood supply to the large nephridia, and with 

 Benham's (6) of that in Lumbricus, though these two authors 

 are not at one as to the course of the blood throuirh these 

 vessels. 



2. — Megascolex goon murk, Spencer. 



Perichaeta goon murk, Spencer. P.R.S. Vict., 1892. 

 Plate XIV., Figs. 2, 2n. 



Dissection. — The dorsal vessel is double (Fig. 2a, D.D.V.) 

 along the greater part of its length. l>nt thirty-one segments 

 from the })Osterir)r end it l)econies single, and at each mesen- 

 tery the t\v(» halves unite as far forward as the front of seg- 

 ment 10, then remain double till the front of 5. where they 

 unite to divide again, joining at the front end, and giving off 

 a comviissurdl vessel on each side to join the ventral, which 

 is single along the wliole length of the body. It is united with 

 the dorsal by a pair of commissural vessels in each setrment at 

 the posterior end, and this arrangement is continued forward 

 as far as segment V^. From the posterior part of segment 12 

 the dorsal gives oft' a supra-intestinal which runs forward to 

 the front of 9, giving oft' in segments 10, 11 and 12 a pair of 

 hearts posteriorly ir> each segment, which run round and join 

 the ventral vessel. I have been unable to find the double supra- 

 intestinal vessel described by Professor Spencer in this form 

 (13). From 9-5 the dorsal gives oft' in the posterior part of 

 eack segment a pair of commissural vessels, and ia 4 one which, 

 after ruianing a short distance, divides into two, one passing 

 forward to the cerebral ganglion to form part of the intestino- 



