Australian Eart/tworms. 217 



From 15-20 it gives off a pair of vessels in each segment, 

 supplying the alimentary canal, but their connections with the 

 ventral (if any) have not yet been made out. Behind the wall 

 opening it continues to give rise to a pair of vessels closely 

 applied to the alimentary canal wall on each side in every seg- 

 ment, but their further relations need microscopically examin- 

 ing. In 14 the dorsal gives off one branch to the sub-intestinal, 

 supplying the alimentary canal on its way, and from the back 

 of 13 a pair of hearts arise, with a double origin — from the 

 dorsal and supra-intestinal — and run round to the ventral 

 vessel, joining it on its under side, this arrangement being con- 

 tinued till segment 10. As far as can be seen microscopically 

 there are valves in the dorsal vessel at each septum, and also 

 at the origin of the hearts. From 9-2 the dorsal gives off from 

 the hinder part of the segment a pair of cnmmissural vessels on 

 each side, and from 9-5 definite branches arise from these to 

 the posterior septum of each segment. The mesenteries in this 

 form are exceedingly thick at the anterior end, and with this 

 fact may probably be associated the great development of small 

 branches arising from all the main vessels in this region. In 

 4 the commissural give off on each side a lateral, running 

 backwards and forming later on, as usual, the suh-iritestinal, 

 which seems to end as a marked vessel at the posterior part of 

 15, but to run on somewhat indefinitely for a short distance 

 behind this. From all around the origin of the lateral, and 

 from the two pairs of commissurals in 2 and 3, small branches 

 arise, supplying the anterior end of the alimentary canal, 

 salivary glands, etc. The lateral gives a definite branch to the 

 hinder septum of the segment in 5-13, which is not so marked 

 in the heart segments as elsewhere ; while there is a particularly 

 large development of branches over the upper portion of the 

 alimentary canal in 9. From 6-15 the sub-intestinal receives 

 vessels from the alimentary canal. 



The supra-intestinal arises in 14, and is double in this seg- 

 ment, and as far as the middle of 13 in the specimen examined. 

 It seems to take origin just where it sends branches to the ali- 

 mentary canal, and from here forwards as far as 8, it sends a 

 pair of vessels in each segment to supply this organ, and open 

 to the sub-intestinal : while in 6 and 7 it o-ives smaller 



