162 



out, or with few, symbiotic algae, and then sometimes within 

 a vacuole. These cells, as said before, are not manifold ; they 

 lodge besides a vesicular nucleus (which is very much like 

 that of the ordinary amoebocytes) and the carmine conglomerates, 

 also often all sorts of detritus and sometimes some unicellular, 

 green algae as described on p. 117, while a single time a va- 

 cuole has been formed round all these foreign parts together. I 

 believe, however, to have a reason for supposing that such vacuoles 

 do occur more often in these cells round those parts than it 

 seems, but that then they are only temporarily invisible by the 

 accidental grouping of the particles. For I have noticed, that such 

 a vacuole entirely disappeared by a movement of the cell (so 

 that its contents seemed to be quite free in the protoplasm), to 

 become visible again a few moments later. Yery often those fo- 

 reign particles are united to a more or less compact mass. Only 

 once I stated such a detritus mass being ejected by a vacuole 

 of an isolated cell. 



In the mean time the sponge itself has lost very much of its 

 red colour in the pure water, while this now in its turn has 

 taken a red tint. As it proves that the sponge does not show 

 any destruction of tissue, we may explain the red tint in the 

 water as caused entirely by the carmine the sponge has (by way 

 of defecation) removed from its body. Now we examine the cul- 

 ture water ; then it appears that the following parts have sunk 

 to the bottom: carmine conglomerates (eg. 7x10, 7 X 13 a^*) 

 together with all sorts of detritus and sometimes a big unicel- 

 lular, green alga, which every time are united to more or less 

 compact masses, just as we found them above within the amoe- 

 boid sponge cells (without symbiotic algae). But there never was 

 an enveloping cell to be seen round these detritus-masses in the 

 culture water. 



So here we have stated in ravel preparations^ that in the fresh- 

 water sponge the function of defecation is performed by amoeboid 

 cells (with few or no symbiotic alyaej, which by means of vacuoles 

 eject the detritus masses outside the sponge tissue^ but which them- 

 selves remain ivithin the tissue. 



