156 



a cell took up the remaining vacuole with the Flagellata in it. 

 At least, one can explain the phenomenon in this way. 



Sometimes one also finds diatoms in the sponge tissue, which are 

 too large to have been ingested by choanocytes and perhaps also 

 by the plasmic layer. These are more likely to have been captured 

 by the tissue bridges and sieve-like membranes of the canals. 



Finally there must necessarily exist a system at the ostia to 

 remove the too large particles kept there, so those which may 

 not enter the incurrent canals ; this need not be accompanied 

 with taking up within the cells. On the other hand, however, 

 it is difficult to think, that food captured in that way should be 

 of no use at all. So here might be still another means of capturing 

 nourishment. I have never seen anything of it. 



So we saw in tJiis chapter tliat in the fresh-water sponges: 

 pt the small (food-) particles are captured from the circulating 

 water within the fiagellated chainbers-, viz. outside-between the col- 

 lars (especially at their base) or between the bodies of the choano- 

 cytes^ ivhile thus, so to sag^ the water is filtered clear (Fig. 63^ 

 65 — 68). Next these particles are taken up within the choanocytes^ 

 united to conglomerates and ejected again into the ^intercellular" 

 plasmic groundsubstance (Fig. 66, 69 — 71), from whence the amoe- 

 bocytes with symbiotic algae take them up in their turn (Fig. 71). 

 2^'^^ the coarse (food-) particles are captured from the circulating 

 water outside and against the fiagellated chambers at the side of 

 the incurrent canal, and such, because they remain sticking in or 

 against the prosopyles. The thin layer of apparently undifferent- 

 iated floiving protoplasm, which covers that side of every fiagel- 

 lated chamber with the exception of the prosopyles (Fig. 72 — 74), 

 then takes up each partiele and carries it off aside into the tissue, 

 so that the prosopyles again become accessible (Fig. 75). If these 

 particles may be of cmy use to the sponge as food, it is very likely 

 that they are carried on to the amoebocytes with symbiotic algae, 

 just as those captured by the choanocytes. 



So we see that it is not right, when Biedermann (6) declares 



