THÉEL, THE AMOEBOCYTES BY ECHINODERMS. 13 



tuhe and which has been fixed immediafely after the ivithdrawal 

 from the tube, we observe the following: 



The scattered or aggregate amoebocytes are more or less 

 intimately bound to the coagulum, but rarely they enter 

 there into a true syncytial union, even when they are densely 

 crowded. The truth is that the pseudopodia of neighbouring 

 cells do not seem to possess in general such a mighty attraction 

 that they, so to say, are forced to fuse. In the event of fusing 

 together and of forming syncytial net-work within the coagu- 

 lum, the net presents a construction almost like that in Pare- 

 cinus — ef. pl. 3, thus different from that in Asterias rubens 

 — ef. plates 3 and 4. 



The comparatively free and loose amoebocytes which 

 occur in the vacuities of the coagulum have a rounded, very 

 little expanded body, provided with innumerable thread-fine 

 pseudopodia running out in all directions (pl. 7, fig. 1). Not 

 seldom the pseudopodia overtwine the central part of the 

 cell, the whole cell getting the appearance of a thin ball or 

 cocoon. 



Again, when the cells are fastened to a film -like part 

 of the coagulum which has been lengthened in one direction 

 artificially by a needle, the cells become highly prolonged 

 in that direction. Consequently, if they are lying close one to 

 the other, the cells assume a puzzling likeness to the bone- 

 corpuscles (pl. 7, fig. 2). 



Here, I will remark that the amoebocytes in question never 

 have come in contact with the wall of the glass tube. According 

 to my opinion, the protrusion of the fine pseudopodia cannot 

 be taken as evidence of a physical process, due to capillari 

 attraction; it ought to be refered to a vital activity. 



Bladder-amoebocytes. 



Blåsamoebocyter Théel.^ 



My knowledge of the bladder-amoebocytes of the holo- 

 thuridea is rather superficial. On the whole, I cannot be fully 

 convinced of their presence in more than two species, viz. 

 Mesothuria intestinalis and Psolus jphaiitapus — ef. text — fig. 3. 

 The truth is that one meets with difficulties to get good and 

 convincing samples of pure coelomic fluid of holothurids. 



^ See Asterias rubens, pp. 15 — 2G; Parechinus miliaris, pp. 27 — 30. 



