46 NILS HJ. 0DHNER, STUDIES ON RECENT CHAMIDAE. 



The circulatory system (fig. 51). The anterior aorta sends its dorsal trunk 

 forward to the left of the stomach and then descends through the foremost part of 

 the liver, where it dissolves into branches, one of them traversing the right side of 

 the oesophagus and becoming ramified in this part of the liver. The descending 

 trunk of the aorta, immediately after its exit from the pericard, gives off a weak 

 collateral to the right which is ramified on the inside of the genital coeca on the 

 right side; the primary trunk also detaches a strong lateral to the left side which 

 passes forward through the liver to the oesophagus, which it follows, giving off some 

 vessels to the stomach, and finally forms the pedal arteria. The chief descending 

 trunk of the aorta passes forward towards the stomach, where it divides, bifurcating 

 on its posterior wall. 



The nervous system is organized in a similar manner to that of the pre- 

 ceding species; thus it is furnished with buccal ganglia and with a pre-pericardial 

 commissure. 



The nephridia (figs. 52, 53) are situated almost symmetrically at the sides 

 of the sub-median intestine. They are extended rather far beyond the latter, the 

 right one being the highest. Both nephridia are pressed together without any se- 

 parating space. The pericard is large and spacious; at the top, round the heart, it 

 has a square section, towards below, however, it grows narrow and finally it is 

 retained only as two lateral funnels, which are situated rather close together. From 

 them there emerge the rather long nephridial ciliated tubes, which are continued 

 by an ampulla or dilatation with folded walls. The pericardial tube then forms a 

 laterally compressed and rather broad channel, turns upwards and luns in the angle 

 of the median and back wall of the outer sac. Having diverged from the 

 opposite pericardial tube, it again describes on the posterior side of the exteriör sac 

 a weak flexure towards the median line and then debouches into the uppermost end 

 of the outer sac. The two outer sacs are strongly lobate and communicate with 

 a short bridge above the pericardial tubes. Their exteriör openings are situated 

 just out of and beneath the latter, and are separated from the opposite genital 

 pores, which appear somewhat higher up. Traces of foot retractors are completely 

 absent in the nephridia. 



The microscopical structure of the gills agrees in the main with the conditions 

 found in Echinochama. Each fold generally contains up to about 23 (sometimes 

 more than 30) filaments. The venous septa alternate with considerably lower ar- 

 terial ones; every third or fifth venous septum is higher, as in Echinochama, but 

 they contain no direct axio-marginal vessels, contrary to the form mentioned. 



