26 ARKIV FÖR ZOOLOGI. BAND 13. N:0 25. 



fluid of the animal is removed into a tubular glass, the forma- 

 tion of a coagulum takes place almost instantly, or by the end 

 of the first minutes, presenting itself as a milky cord along 

 the middle of the tube. It is inconceivable that siich a sud- 

 den change of the liquid can be due to the activity of the 

 amoebocytes alone, all the more so, as the corpuscles are few 

 in proportion to the superfluity of the liquor itself. By mi- 

 croscopic examination of a fresh sample of such a coagulum, 

 we can satisfy ourselves that the plasma-amoebocytes are 

 in such a minority that they impossibly could give rise to a 

 coagulum of such extension. To my mind, the phenomenon 

 in question can be explained only by the presence of an abun- 

 dance of fibrin-matter in the coelomic fluid. As previously 

 emphasized, the coagulation ought to be impulsed by the 

 coelomic fluid having been brought to a standstill in the 

 tubular glass. 



A sample of the coagulum of Mesothuria having been 

 removed from the tubular glass, suitably fixed and stained, 

 the fibrin-like substance shows structural distinctions in 

 various places of the preparation. In o ne spöt, it is repre- 

 sented by a hyaline film of considerable extent, even or 

 wrinkled in such a manner, that the film gets the aspect of 

 being crossed by fine filaments, separated or in bundles; here 

 and there plasma-amoebocytes adhere to the film. Other 

 parts of the preparation show themselves to be traversed in all 

 directions by coarser or finer threads and filaments, isolated 

 or j oined in bundles. Mixed among these two different fi- 

 brinous structures, one meets fine-meshed net-works of fibrin 

 and scattered or crowded corpuscles of different kinds — ef. 

 pl. 7, fig. 2 and text-figures 5 and 6. 



It seems to me that par. III of Tait's and Gunn's^ »Sum- 

 mary of Section IV» on coagulation of crustacean blood cor- 

 responds very well to the statement above. For on page 72 

 they say: »The coagulation-products take the form either 

 of long strings of fibrin or of more expanded masses. This 

 form probably depends on the course taken by the thrombin 

 as it issues from the cells according as it is carried in stream- 

 lines by currents, or allowed to diffuse uniformly and gradu- 

 ally from each separate source. » 



I am convinced that the different structures of the coagula- 



' Op. cit. j 



