175 



called intercellular ground-substance , is in fact performed by 

 amoeboid cells. 



In connection with what was said on p. 170 we can put tlie 

 question again, if in fact there is in principle any difFerence 

 between all those various kinds of amoeboid cells, which — 

 appearing in the living sponge as undifFerentiated plasmic substance 

 (p. 168) — on the one side, as we saw, capture coarse (food-) 

 particles from the water (p. 152, 156, 174) or lodge them (p. 149 — 

 150, 153 — 154), on the other side perform the function of defe- 

 cation and excretion (p. 163 — 166, 169 — 170), and in the third 

 place form the „intercellular" groundsubstance of the parenchyma 

 (p. 171 — 174). I suppose to have to answer also this question 

 negatively. They are more likely to be all the same cells, each 

 kind only temporarily performing another function. See also 

 p. 170—171. 



And at last the question, if these amoeboid cells — which, as 

 one knows, lodge but few or no symbiotic algae — are perhaps 

 identical to the amoebocytes with numbers of symbioti-c algae, 

 again differing from them only by a temporarily other function. 

 Also this would be possible (cf. p. 149, 162). But I do not 

 venture to answer this question; I only want to ask. See also 

 Weltner (68). 



II. 



One must not confound the often mentioned food-(digestion-) 

 vacuoles of the amoebocytes with symbiotic algae (p. 94 — 97, 

 111) and the defecation and excretion vacuoles of the amoeboid 

 cells without symbiotic algae (p. 162 — 166) with a peculiar 

 vacuolising of the tissue of the outer, and sometimes also the 

 inner sponge surface, which gets something of a foamy structure 

 by it. I mentioned it already on p. 17, and such with regard to 

 a similar structure in isolated amoebocytes (Fig. 4). I think that 

 this last kind of vacuoles will properly not belong to the cells, 

 but are rather parts of the surrounding water, which were tem- 

 porarily enclosed by the pseudopodia during the amoeboid motion 



