Australian Earthivorms. 79 



19. — Diporochaeta bakeri, Fletcher. 



Perichaeta bakeri, Fletcher. Proc. Linn. N.S.W., 



vol. ii., 1897. 



Plate XVI., Fig. 19. 



Dissection. — Dorsal vessel single, running forward to break 

 up in segment 1, and joining the ventral by a commissural 

 vessel on each side at the most posterior end. It is swollen 

 in 10-17, and connected with the ventral by a pair of com- 

 missurals in each segment, till the posterior part of segment 

 12, where it gives off a supra-intestinal, running forward to 

 break up in 8. The supra-intestinal apparently receives u small 

 branch from the dorsal on each side in 10 and 11, and in 10, 

 11 and 12 from the back of the segment, at the junction of 

 the branch from the dorsal with the supra-intestinal arises a 

 Veart on each side. In segments 9-5 commissurals arise from 

 the dorsal, and pass to the ventral vessels, giving blanches to the 

 ventral body-wall (Br.AV.) on the way. In segment 4 this vessel 

 from the dorsal seems to end on the alimentary canal wall, and 

 in 6 it apparently gives off a branch, running backwards as the 

 lateral, though the point of junction in the specimens examined 

 was not very clear. The lateral runs on as the suh-intestinal 

 on each side, in 10, 11 and 12 receiving branches from the 

 alimentary canal, derived from the supra-intestinal, and ending 

 on the posterior mesentery of segment 13. 



The ventral is single along the whole length of the body, 

 breaking up in segment 1, and appearing to give branches t# 

 the ventral body-wall behind the hearts. 



From the foregoing description it will be seen that, as far as 

 may be stated from the limited number of worms examined: — 



1. The number of hearts seems to be fairly constant, three 

 being the usual ; but they may tend to increase as in P. 

 dorsalis, P. coxii and P. fielderi, the last showing thiv«5 charac- 

 teristic markedly. Beddard (1) remarks that the j^osition of 

 the last heart is not a character subject to variation. 



2. That the hearts may be always distinguished from mere 

 swollen vessels by their connection with the supra-intestinal, 

 except in the case of D. davallia, as described. 



