EXCRETORY SYSTEM OF THE EARTHWORM 143 



containing its own nephridium, so that waste matters of any one 

 somite are expelled to the outside by the nephridium of the 

 next posterior somite. The nephrostomes or mouths of the 

 nephridia are flattened fan-like structures consisting of two 

 flattened lamellae or plates with a narrow slit-like opening be- 

 tween them, the great cells lining the opening are covered with 

 powerful cilia which maintain a constant current toward the 

 tubular part of the nephridium. These tubes are developed in 

 coils which lie in the posterior parts of the somites, three coils or 



2T 



FIG. 58. Nephridium of Lumbricus. /, Funnel or nephrostome; ds, dissepi- 

 ment; n.t., narrow tube, ciliated between a and b; m.t., middle tube; w.t., wide 

 tube; m.p., muscular part; ex, external opening. (From Sedgwick and Wilson, 

 j.fter Benham.) 



mrns in each, the third ending in an enlarged portion opening to 

 the outside on the ventral wall of the somite (Figs. 55 and J8). 

 All of the turns are richly supplied with blood vessels. 



If carmine powder is injected into the coelom it is taken up by 

 the chlorogogue cells which then break down freeing the car- 

 i nine together with fragments of the chlorogogue cells, and all 

 rre caught up by the current made by the nephrostome and 

 ( arried through the nephridium to the outside. From this ex- 

 periment the conclusion has been drawn that the waste matters 

 ( >f the tissues are brought in the circulation to the chlorogogue 

 c ells and acted upon by the fluids of these cells. The products 



