NEW ENGLISH GENUS OF AQUATIC OLIGOOH^TA. 169 



appears to commence with the intestinal region in Somite ix, 

 in front of which a capillary network of the ordinary character 

 exists. The constituents of this network enlarge, the meshes 

 are thereby reduced, and a gradual coalescence and disappear- 

 ance of the walls gives rise to a sinus. In Somite viii and 

 partly in Somite vii a plexus appears superposed on the sinus, 

 with which it communicates, the plexus being a very close one 

 and the vessels large. More anteriorly the sinus is absent, 

 and a plexus of capillaries only surrounds the gut. 



The blood-supply of the pharynx is derived, as above men- 

 tioned, from a network, with which the dorsal and lateral 

 vessels communicate ; the commissural vessels do not, as far 

 as I can ascertain, give any branches to this plexus — they run 

 round the oesophagus to the ventral vessel. This pharyngeal 

 plexus is continuous with the oesophageal plexus just described. 



The lateral hearts of Somites xi, xii, give off a branch to the 

 sperm-sacs. 



The present worm is, then, remarkable on account of («) the 

 perienteric sinus, and (b) of the longitudinal tegu- 

 mentary vessels. 



(a) The sinus, which is similar to that found in many mud- 

 loving and tube-forming Polychsetes — as, for example, Sabellids, 

 Arenicola, &c. — occurs but rarely among the Oligochaeta ; 

 in fact, outside the family of Enchytrseidse it is practically 

 unknown, or at any rate unrecorded. Vejdovsky, in his 

 ' System und Morph. d. Oligochaeten,' represents a transverse 

 section of Allolobophora cyanea on pi. xvi, fig. 22, in 

 which a sinus surrounds the intestine ; again, in fig. 8 of the 

 same plate, illustrating Dendrobaena rubida, a sinus is 

 represented around the gut ; but he does not label this, and it 

 may be merely a diagrammatic representation of the ordinary 

 plexus. Again, on pi. xiv, figs. 2 and 9, two transverse sec- 

 tions through Criodrilus show a perienteric sinus labelled 

 " rfs.," which letters indicate " Gefassschlinge des Magen- 

 darmes" according to the explanation of the plate. 



In the body of the work I find no specific mention of any 

 sinus, though in reference to AUurus, Dendrobaena, &c., 



