106 



side the weakened power of resistance of the algae — in conse- 

 quence of them ■ being in the sponge in darkness, lacking food 

 and O2 and with accumulation of C 0^ — , on the other hand 

 the still stronger hurtfull influences from the side of the sponge 

 cells (point I, 1, 2) — also in consequence of them being in 

 darkness — are the causes, that such a great number of those 

 algae die in the amoebocytes in darkness. 



Why only so few algae die (point II, 5) in a sponge in light 

 with regard to the total number present, is also quite clear after 

 the preceding. The power of resistance of the algae will be much 

 higher here, in light, than in darkness. The hurtful influences 

 from the side of the sponge, also by "^rt^i^ "^already less forcible 

 now, will thus destroy much fewer algae in this case than the 

 sponge, which remains in the dark. But there will still always 

 be a small number of algae, that disposes of less power of resist- 

 ance for some or other reason ; this will have to be destroyed 

 by the sponge (compare II, 8). 



Also the other facts mentioned sub II, 1 — 8 are very well 

 compatible with this solution. 



At last we get to the question, what those hurtful influences 

 from the side of the amoebocytes, which proved able to kill the 

 living algae with weakened resistance, are exactly. Whether they 

 are : simply (point I, 1) a killing from want of food, so a certain 

 feeding-process of the sponge cells; or (point I, 2) a „poisoning" 

 of the algae by hurtful products of metabolism of those cells, 

 consequently something, which in fact would have nothing to do 

 with the direct feeding process of the amoebocytes, but for instance 

 should be more considered as a reaction of defence of the cells 

 against an intruder ; or, as we have just formulated above, both 

 causes together. In all three the cases, however, the final result 

 remaii^s the same, namely that the algae killed in one of the 3 

 ways are digested at last by the amoebocytes. So this question has 

 in fact not much practical use ; it is more of theoretical interest, 

 as I remarked above. 



Also, no definite answer can be given for the present; there 

 are arguments for both points (I, 1 and I, 2). This can be shown 



