Audrallan EarthAvonns. 71 



the alimentary canal on the way. This arrangement apparently 

 persists in the last segment, and is continued forward in each 

 to the region of the swellings in the dorsal vessel. 



In segments 9, 8, 7, 6, 5 and 4, a commissural arises from 

 the back of the segment on each side. In segment 5 this vessel 

 divides into two after a short distance, one half running for- 

 ward to break up in the salivary gland ; and one passing back 

 as the lateral, forming a double sub-intestitial in 10, 11, 12 and 

 13, and ending in 13. In these segments it receives branches 

 from the plexus on the alimentary canal, derived from the 

 supra-intestinal, which rises from the dorsal in the hinder part 

 of the segment 14, and runs forward to the front of segment 

 8, receiving a small branch from the dorsal in 10, 11, 12 and 

 13 on each side, and giving off from the point of junction of this 

 in each of these segments a pair of hearts to the ventral 

 vessel. The most anterior of these is smaller than the others, 

 and there seems to be a tendency to a more than ordinary 

 development of hearts in this species, as, in addition to the 4 

 pairs commonly met with in M. fiehleri, a s'ngle heart was 

 found in one specimen in segment 14 on the left side (c£. Bed- 

 dard, 1). In 14 there seems to be no commissural, but a vessel 

 arises from the supra-intestinal apparently ending on the ali- 

 mentary canal wall. 



The ventral vessel is single, and runs forward to break up 

 segment 1. 



Sections. — The blood supply in the heart region is fairly 

 simple. In the interior part of each segment the dorsal vessel 

 gives off a pair of small branches with valvular openings (Fig. 

 24, v.), to the supra-intestinal, and from, or close to, the junc- 

 tion of those two the supra-intestinal gives off a pair of hearts, 

 their openings being guarded by valves. The hearts join the 

 ventral vessel on its under surface by a valvular opening. The 

 supra-intestinal gives oft* a branch to the alimentary canal, 

 forming a thick plexus ou its walls (PL), from which a main 

 vessel passes on each side to the sub-intestinal. In the region 

 of the hearts the nephridia are micro-nephric, and the origin 

 of their blood supply is indefinite, but is probably from the 

 ventral vessel or its ventro-tegumentary branches. At the 

 hinder end, where the excretory organs are meganephric, they 



