THÉEL, THE AMOEBOCYTES BY ECHINODERMS. 25 



thurids. In his »Observations upon the chemical composi- 

 tion and coagulation of the blood of Limulus polyphemus, 

 Callinectes hastatiis and Cucumaria sp. he wrote with regard 

 to the last: »Specimens of the perivisceral liquid allowed to 

 stånd in watch-crystals give an imperfect coagulum, the cor- 

 puscles settling to the bottom as a membranous-like sedi- 

 ment. The imperfect coaguhim is formed by the fusion of 





^ * J^r^'^ *:^# 





Text-figiir 6. Another piece of the same coagulum as in text.-fig. 5 and 

 treated in the same way. A few strings and filament of fibrin are visible, 

 but a good deal of plasma-amoebocytes are present, free or adherent to the 



filaments or net-work. 



the amoeboid white corpuscles or of thick pseudopodia which 

 arise from them». This statement of Howell may be true, 

 but with reservation; for my own investigations have led me 

 to the conviction that the coelomic liquid of almost all holo- 

 thurids contains a fibrin-like matter, too, though many times 

 so sparingly that it scarcely can be revealed. 



In Mesothuria intestinalis, on the contrary, the fibrinous 

 substance of the coelomic fluid, apart from its cell-elements, 

 is present in such an abundance that it takes the leading part 

 in the coagulation process. When, for instance, the coelomic 



