NEW MAT, TO PIT AT, A. 173 



into the abdomen. The niesotlioracic ganglion is 

 smaller than the last one, but, except that the lateral 

 edges are more nearly equal, is very similar to it. Its 

 anterior side joins the posterior side of the one in front, 

 and from its lateral angles trunks arise that supply the 

 niesotlioracic legs. The prothoracic ganglion is more 

 elongated than the others and the lateral angles are 

 relatively farther l>aek, but as before, the leg branches 

 arise from them. There are no interganglionic com- 

 missures between the thoracic ganglia but the protho- 

 racic ganglion is connected with the subtesophageal 

 ganglion by two short, longitudinal trunks. In other 

 forms the thoracic ganglia are a little more separated, 

 but in all cases known, the nervous system is much 

 concentrated and ganglia never occur in the abdomen. 

 Longitudinal sections of Menopon titan (plate x, fig. 1) 

 show that the thoracic ganglia (g\, g-, and .73) are oval 

 longitudinally and have an outer layer of large cells like 

 those in the head. Transverse sections of Menopon sp. 

 (plate xii, figs. 5-7) show that each ganglion (^^i and (/.) 

 is double and very large. In Euryinetopus taurus (plate 

 xvi, fig. 7) each ganglion is supplied with tracheae 

 from a large, transverse commissure (i r) passing trans- 

 versely from one main, lateral, tracheal trunk to the 

 other. Each of these transverse trunks is applied very 

 closely to the j)osterior part of the corresponding gan- 

 glion, and gives off into the latter numerous ramifying 

 branches. 



V . T H E D O K S A L A^ E S S E L. 



The heart was first described by Wcdl in 1:S55. 

 Nitzsch says nothing about it. Kramer in 1S69, 

 briefly described that of Lipeurus Jejunus. Grosse 



