547 



sea-water in which living colonies of Alcyonium were kept. By 

 means of a pipette, clouds of carmine were squirted about the ex- 

 panded polyps. After three days thin free-hand sections were cut and 

 examined as before, when minute particles of carmine were seen in- 

 cluded in the endoderm cells lining the walls of the polyp. 



It is interesting to note that some of these cells were seen to slowly 

 thrust out one or more pseudopodial processes i. e. to enter an amoeboid 

 phase. (Endoderm cells of the polyps with pseudopodial processes 

 were also observed in microtome sections of preserved specimens of 

 Lohophytum densum after staining with borax carmine or Delafield's 

 Haematoxylin.) 



After 4 — 7 days (the time varied in individual colonies) minute 

 particles of carmine were observed 



1) in the cells of the endoderm canals in the mesogloea 



2) - - - - - solid cords of endoderm in the mesogloea (in 

 both instances some of the cells were seen to become amoeboid) 



3) in the stellate and spindle shaped cells of the mesogloea (see 

 fig. 4 in which the carmine particles are shown in black). 



The conveyance of solid particles of carmine from the cavity of 

 the coelenteron of a polyp to portions of a colony apart and even 

 remote from the polyps, the fact that the endoderm cells frequently 

 become amoeboid, and the "amoeboid" character of the mesogloeal 

 cells afford substantial evidence that the socalled "nerve cells" of the 

 mesogloea are endoderm cells which have become amoeboid and 

 wandered into the mesogloea. 



As a stimulus affecting one polyp may be transmitted with gradu- 

 ally diminishing effect to its neighbours, it is probable that stimuli or 

 impulses travel through the system of amoeboid cells, but the presence 

 of carmine in these cells naturally suggests that they may also take 

 up food or excreta. It is very probable that the amoeboid cells are 

 nutritive and excretory as well as nervous in function, and may 

 therefore be looked upon as neuro-phagocytes. 



It is well known that in the embryonic stages of higher forms of 

 life, ganglion cells have a certain power of movement through the 

 tissues, but we have no reason for believing that nerve cells retain 

 this power when maturity is reached. 



As we have no experimental evidence that the Alcyonaria are 

 more nervously sensitive than other lowly organised groups, it seems 

 impossible to regard this extremely well developed system of amoeboid 

 cells with coalescing pseudopodia as a specially differentiated "nerve 

 plexus". 



In their amoeboid character and multiple functions, the stellate 



37* 



