174 



quite independent of the former. I too found in living- tissue the 

 amoebocytes with symbiotic algae and the cells with equally 

 large grains imbedded in an apparently undifferentiated inter- 

 cellular piasmic ground-substance (p. 17, 146 — 148, 156, 168, 

 Fig. 69, 71), in which numbers of enclosures (eg. oildroplets 

 and sometimes symbiotic algae) and also vacuoles (p. 163 — 165), 

 and which, at the side of the canals, was one time lined by 

 cells (eg. pinacocytes) and not so another time (p. 154). When 

 rubbed to pieces as well as when warmed, or after killing and 

 macerating, tJie whole tissue^ so also that undifferentiated piasmic 

 substance^ jrroved to consist of ainoeboid cells ivith nucleus (see 

 also p. 153—154, 169—170). 



As to the observation, that that piasmic substance (i. e. the 

 ground-substance of the parenchyma) was not entirely lined with 

 pinacocytes, I mentioned already on p. 154 that the possibility is 

 not excluded that pinacocytes were present in fact, but not to 

 be discovered by their fine extension. With regard to the above 

 described phenomena of ingestion of food in the flowing piasmic 

 layer outside and against the flagellated chamber (p. 152) and 

 of defecation by vacuoles in the excurrent canal walls (p. 163 — 

 166), it seems more likely that, at least there where those pro- 

 cesses take place, the pinacocytic covering of the canals will be 

 missing. For that would certainly advance the rapidity. On the 

 other hand my observation made during the capturing of coarse 

 food particles outside and against the flagellated chamber, viz. 

 that first the particle remains quiet for about 10 minutes before 

 being carried off by the flowing piasmic layer (p. 152), might 

 possibly show that thin pinacocytes, which then must first be 

 passed by the food particle, are present. 



As we have now seen that all apparently undifferentiated pias- 

 mic ground-substance consists of amoeboid cells, we may conclude 

 that the layer of flowing plasm at the outside of the flagellated 

 chambers (p. 152, 156) is also formed by such cells. And we 

 may also conclude that the (food-) transport (from the choanocytes 

 to the amoebocytes with symbiotic algae, for instance) which, as 

 we saw above (p. 146 — 148, 168), takes place through the so 



