PHAGOCYTOSIS IN PERIVESICAL FLUID OF ARBACIA. 147 



hsematoxylin. A large nucleolus is also present. When fixed 

 with Schaudinn's fluid and stained with Haidenhain's hacma- 

 toxylin, the cytoplasm appears reticulate (Fig. 2). 



I. PHAGOCYTOSIS. 



Carmine and india ink suspensions in sea-water w r ere used in 

 order to determine the extent to which the leucocytes took part 

 in the inclusion of foreign particles from the perivisceral fluid. 

 One cubic centimeter of sea-water suspension of finely powdered 

 carmine \vas introduced into the perivisceral fluid through a 

 perforation in the peristomial membrane. The individual so 

 treated was put back into the aquarium and at the end of thirty 

 minutes a drop of the perivisceral fluid was examined. Although 

 a large number of carmine grains were yet free in the plasma, 

 it was observed that all of the leucocytes had taken up one or 

 more particles. At the end of an hour another examination was 

 made of the perivisceral fluid and at this time the plasma was 

 comparatively free from carmine particles and the leucocytes 

 were heavily loaded with them. The ingestion of several of 

 these particles by the leucocyte was observed. This individual 

 was kept in the aquarium for two weeks during which time the 

 perivisceral fluid was examined at intervals. At the end of 

 two weeks some leucocytes containing carmine particles were 

 still present in the perivisceral fluid. This fact indicates a period 

 of longevity on the part of these cells, but the fate of the large 

 number which performed the function of phagocytes is still in 

 doubt. Ribaucourt suggested that after they had become 

 loaded with waste material from the perivisceral fluid they made 

 their way into the ambulacral system by diapedesis and thence 

 passed out through the madrepore. Since, however, no currents 

 have been observed nor any cells observed leaving the madrepore, 

 this assumption is unconvincing. The problem of excretion 

 and with it the fate of the old phagocytes has yet to be solved. 



The results obtained by the injection of I c.c. of india ink- 

 sea-water suspension were the same as those obtained with the 

 carmine suspension. And further in the study of the clot, it 

 was observed that the ingestion of particles by the leucocytes 

 does not inhibit their activity in the formation of the clot. 



