242 JAM1.S KRNKST KIXDRED. 



From their activities they must be recognized as the most gen- 

 eralized cells in the perivisceral fluid since no others have been 

 observed whose functions are so diversified. The question of 

 their origin is a vexing one, although it was once pointed out 

 th.it the dorsal organ may, in the Asteroidea, be an organ of 

 leucoblastic function, a function which Cuenot ('oi) denies this 

 organ, claiming that it is more likely an organ for the elimination 

 of wornout cells of the perivisceral fluid and that the "amcebo- 

 rytes" (general term) are probably peritoneal in origin and may 

 also arise from each other. In all probability the number of 

 leucocytes increases rapidly when an animal is injured, particu- 

 larly in the region of the injury, where they form the framework 

 for the regeneration of other tissues. They may be regarded as 

 one of the important agents in the replacement of lost parts in the 

 Echinoderms. 



FIG. 26. "Amcebocyte with red spherules," Strongylocentrotns drobachiensis. 



cam. luc., X 1300. 



FIG. 27. "Amcebocyte with red spherules," S. franciscanus, cam. luc., X 1300. 



FIG. 28. "Amcebocyte with red spherules," Echinarachnius eccentricus, cam. 

 luc., X 1300. 



FIG. 29. " Amoebocytc with yellow spherules, " E. eccentricus, cam. luc., X 1300. 



2. The "Amcebocytes with Spherules.'" 



There are two groups of "amcebocytes with spherules" present 

 in the perivisceral fluid of the Echinoderms. One group of these 

 is characterized by the presence of pigmented spherules in the 

 cytoplasm and the other by colorless spherules. In both types 

 the spherules fill the cytoplasm to such an extent tli.it the nucleus 

 appears merely as a light space in the center of the cell. All of 

 the "amcebocytes with spherules" are further characterized l>\ 

 the presence of very blunt pseudopodia and when fluid con- 

 taining them is allowed to stand they tend to assume a spherical 

 shape. 



Amcebocytes containing red spherules were observed in the 



