12 ARKIV FÖR ZOOLOGI. BAND 13. NiO 25. 



are very thin and scattered, Singularly enough, Cucumaria 

 lactea is totally in want of red blood-corpnscles, and an exa- 

 mination of its plasma-amoebocytes does not seem to reveal 

 any new views of interest. 



Psolus phantapus. 



The amoebocytes are numerons and often tend to fuse 

 together in order to result in the formation of rather large 

 syncytial net-work on the glass slide. Scattered among them, 

 there occurs a niimber of hyaline, minute spheres together 

 with somewhat larger, glassy, irregularly formed corpuscles, 

 which are capable of changing form incessantly. Both of them 

 seem to be in want of a nucleus. Their task is qiiestionable, 

 and I should not wonder, if they proved to be strangers to the 

 coelomic fluid. 



Stichopus tremula. 



In proportion to the voluminous body of the animal 

 and the enormous quantity of its coelomic fluid, the plasma- 

 amoebocytes are insignificant and very scarce. The polian 

 vesicle is often crammed with fine-grained, non-cellular mat- 

 ters, and encloses, besides, a niimber of oval, fusiform, pjrriform 

 or rather tape-like, hyaline corpuscles, which present some 

 resemblance to those in Tliyone. Devoid of a nucleus they 

 vary in length from 11 »j. to 41,8 {J^- Probably they are notliing 

 but fragments of shattered tissues. 



Mesothuria intestinalis. 



An examination of a sample of the coelomic fluid reveals, 

 that the plasma-amoebocytes are proportionally scarce and 

 that their syncytia are thin and scattered. They present 

 themselves in all states from fusiform and thread-like to flatte- 

 ned and discoidal. The syncytia are insignificiant, and com- 

 monly made up of less than 15 or 20 cells. 



If the perivisceral fluid of Mesothuria is removed from 

 the animal and is brought to a standstill in a tubular glass, 

 it undergoes remarkable changes and coagulates almost in- 

 stantly, the coagulum forming a meshy cord aiong the middle 

 of the glass tube. When examining that part of the coa- 

 gulum, ichich has not been in contact with the ivall of the glass 



