E. MAESHALLI. — THESOCYTES. 173 



lliesocytes. 



(PI. IV, iig--. Sy-ij; n. V, fig. 3G; Ih.) 



Some facts concerning this kinJ of cells have already been 

 given apropos of the ' Knollen ' cells described by F. E. Schulze 

 from the trabeculse of Schaudinnia ardica (p. 156). Besides 

 that investigator, Marshall also seems to have seen the same 

 cells in HoUenia ('75, p. 104; pi. xill, figs. 3-6). 



In general the thesocytes are plump-bodied but rather 

 irregularly shaped cells inclosing fat-like granules or globules, 

 amongst which the nucleus is always demonstrable. In the 

 details of their appearance they vary somewhat in difiereut 

 species. For example, in Itossella longisp'ma Ij. the fat-like 

 substance appears to fill up the cell in a single mass (measur- 

 ing, say, 10-20," across), pressing the small nucleus against the 

 thin investing membrane. In Rhabdocalyptus vlclor Ij. and R. 

 capillatus Ij., it is accumulated in the form of a small number 

 of variously sized spheres, which take up nearly the entire space 

 of the cells (7-15 it, sometimes 20 n, in diameter) ; together with 

 such cells there occur others in which the reserve-matter is 

 apparently breaking up or has been nearly entirely resorbed. 

 AcanthasGUS cactus F. E. Sch. shows the thesocytes in unusually 

 large numbers, scattered on the ti'abecular beams as well as on 

 the dermal and gastral membranes. They may be described as 

 compact masses (measuring 8-20 /< across) of small and uniform- 

 looking spherules (about 2/'. in dia.), which are well preserved 

 in all hardened specimens, generally concealing the nucleus 

 amonost them. Heie acain we occasionally meet with such 

 thesocytes as have the spherules evidently in different stages of 

 disintegration and of resorption. This process consists in the 



