74 G'Wijnnetlt Biichauan : 



14. — Megascolex coxii, Fletcher. 



Pepichaeta coxii, Fletcher. Pioc. Linn. Soc. N.S.W,, 



1888. 



PhiteXV., Fig. 14. 



Dissection. — Dorsal vessel single, swollen in segments 10-15. 

 though not much so. It runs the whole length of the body, 

 and in segment 1 divides into two, passing round on each side 

 to join the ventral vessel. Tlie dorsal and ventral are also ap- 

 parently connected as usual at the posterior end, the dorsal 

 giving off a pair of commissural to join the ventral in each 

 segment, as far forward as the region of the hearts. In 14 and 

 15 these branches are two in number at their origin from the 

 dorsal, though it is not clear if both reach the ventral. This 

 latter becomes double in segment 14 in one specimen examined, 

 but this is probably only an individual variation, as it was not 

 noticed in the other, nor in any other species. In the hinder 

 part of segment 13 the dorsal gives off a pair of hearts to the 

 ventral, joining it on the under side, and this arrangement is 

 continued forward to 10, the cnlj- other worms in which four 

 pairs of hearts were observed being- P, fielder i, F. dur sails and 

 C. grandis (see Beddard, 1). That in segment 13 may be said 

 to give rise to the supra-intestinal, which runs forward to the 

 front of 7, or, the hearts may be taken as having a double 

 origin, but the supra-intestinal does not appear to run back 

 beyond the first pair, seeming rather to arise from the dorsal 

 through them. From the back of 9-4 the dorsal gives oft* in 

 each segment the usual cumniissuraJ re.^sel-s, which send 

 branches to the ventral body-wall (B.W.) in 9-6. In segment 

 4 the commissural gives off close to its origin a media ji vessel, 

 whicli runs back to break up in a large plexus over the alimen- 

 tary canal in segment 5. The whole of the anterior part of the 

 digestive tract and the salivary glands are particularly well 

 supplied with blood in this form, especially in segments 4, 5 

 and (). In segment 3 a vessel arises from the dorsal, but ap- 

 pears not to reach the ventral, while from the commissural in 

 segment 4 arises, on each side, as well as the median, a 

 latirol vessel, which sends branches forwards to the salivary 

 gland, and one backwards, forming later on the sub-intestinal. 



