906 REPORT OF COMMISSIONER OF FJSH AND FISHERIES. [28] 



D.— VASCTJLAE SYSTEM. 



The vascular system of Tuhificidm takes an iutermediate place be- 

 tween those of Enchytrceidce and Lumhricididce. It is more complicated 

 than in the former family, but less so than in the latter. 



The main truncs are found to be a ventral vessel and a dorsal one. 

 The former is forked in the fourth setigerous segment, the latter con- 

 tinues entire to the cephalic lobe of the body. Only the dorsal vessel 

 is pulsating. Besides the above primary vessels we find three other 

 kinds, viz, gastric, perigastric, and dermal. 



The gastric vessels, again, are of two kinds, viz, secondary and tertiary. 

 The secondary gastric vessels are in every segment two, and situated 

 near the anterior dissipiment of the segment, one on each side of the 

 body. They are found to closely embrace the gastric canal, hence their 

 name, and serve to directly connect the ventral and dorsal vascular 

 truncs. 



From these secondary and gastric vessels we find numerous others, 

 very minute ones, spreading and branching on the alimentary ^ianal ; 

 they serve eminently to carry the blood to this organ, and are most 

 likely present in all the species of the family. 



Of the perigastric vessels we also find one pair in every segment, but 

 situated behind the gastric pair. In the same way as this latter ivt 

 connects the ventral and dorsal vessels with each other, but is narrower, 

 longer, and its windings are more irregular. As their name implies, 

 their chief function is to supply the perigastric cavity with blood, and 

 partly, also, the sexual organs suspended in the same cavity. Thus 

 we find always the perigastric vessels much larger and longer in those 

 segments which contain receptacles and testes, &c., and their windings 

 are oftentimes inseparably united with the latter organs. Such is 

 especially the case in Telmatodrilus and Ilyodrihis. 



The perigastric vessel in the seventh setigerous segment is generally 

 considerably dilated, shows a strongly pulsating movementi, and takes 

 evidently the function of a heart. Of such hearts I have never found 

 more than one pair in each worm. 



In Telmatodrilus and Ilyodrilus, however, the perigastric vessels are 

 not dilated, and no distinct hearts can be said to be existent in those 

 worms. A substitute is, however, found in the great extension of the 

 perigastric vessels in some of the anterior segments. In Telmatodrilus 

 it is the perigastric vessels in the tenth to the sixth setigerous segments 

 which are thus unusually long. Those of the tenth setigerous segment 

 are the longest, and that part which is situated nearest to the dorsal 

 vessel the thickest ; that part, again, which is nearest the ventral vessel 

 is vanishingly minute, and any pulsation in this part nearly impossible. 

 Each anterior pair of those perigastric vessels is smaller than the poste- 

 rior pair, and in the fifth setigerous segment the pair has again assumed 

 its normal size. 



In Ilyodrilus the perigastric vessels in the nine first setigerous segments 



