236 JAMES ERXEST KIXDRED. 



elements of a synrytium and it is this syncytial formation which 

 is their most valuable vital activity, in that it is concerned with 

 the repair of injury and the replacement of lost parts in the 

 organism. This is due to the fact that these syncytia close 

 wounds and form the basis for the growth of the other tissues 

 and further that these cells themselves may take part in the for- 

 mation of other tissues. 



Theel ('21) states that there is a fibrin-like substance which 

 occurs in the coagulation of the ccelomic fluid in the Holothuroi- 

 dea in addition to the meshwork of the fibers formed by the ar- 

 borizing leucocytes. That this fibrin-like substance is extra- 

 cellular is evidenced by the fact that a fibrous meshwork occurs 

 when there are far too few cells to form such a meshwork so 

 rapidly, by leucocytic syncytia alone. I observed this super- 

 fluity of fibers in the drops of perivisceral fluid of all of the prepa- 

 rations of fresh material and was at a loss to account for it. The 

 origin of this fibrous substance is not known, although it has 

 been suggested by Schafer ('83) that it might have been secreted 

 by the leucocytes. That it does not coagulate in the fluid in 

 the perivisceral cavity is due to the various ciliated cells which 

 keep the fluid in motion (Cuenot, '01). This movement of the 

 perivisceral fluid does not prevent the formation of plasmodia or 

 syncytia, but it does seem to inhibit the fibrin-like coagulum. 



From the observations of Theel and others it is well known that 

 in the development of the test of the Echinoidea the leucocytes 

 form syncytia within which is secreted (intracellularly) the 

 spicules which fuse and form the stereom, a definite beam and 

 rafter skeletal structure. Leucocytes containing spicules have 

 been observed in the perivisceral fluid of various Echinoderms. 

 I have observed them in the perivisceral fluid of Henricia levins- 

 cula (Fig. 16). Theel from his observations on the occurrence 

 of these cells containing spicules is of the opinion that we may 

 presume that the skeleton of the Echinoderms is due to the 

 activity of migratory " plasma-amoebocytes " and their syncytial 

 fusion. This assumption may be true, but there has been no 

 evidence presented which shows that these cells (my leucocytes) 

 are concerned in the replacement of resected areas of the stereom . 

 Hence in order to determine the scleroblastic activity of the leu- 

 cocytes a series of resections of the test of S. drobachicnsis were 



