1066 



water, we are forced to the conclusion, that from the point of view 

 of usefulness to the alga the association with the sponge can 

 certainly not be called a symbiosis in the sense of that found in 

 the lichens. 



/?. Concerning the question of the advantage to the sponge of 

 this association with the alga, I have been able to establish a verj' 

 large number of facts, too numerous to give here. With the aid of 

 these I came to the following view on this question : 



It is either the need of food for the part of the sponge or (and) 

 the "'toxic" action of harmful metabolism-products of the sponge (to 

 be considered as a defensive reaction against an intruder), which 

 continually destroys the green "symbiotic" algae in the amoebocytes; 

 and exactly those algae whose power of resistance has been 

 weakened already by some cause or other. All the algae so destroyed 

 serve the sponge a.s food; because this one digests and dissolves them 

 entirely either free in the protoplasm of its amoebocytes or in 

 food-vacuoles, retains the decomposition-products, and builds up its 

 own cell partis with I hem, for instance oildrops and carbohydrate 

 globules. These oildrops and carbohydrate globules in their turn 

 i\re the source of the great quantity of energy, which the sponge 

 transforms in the movement of the flagella in the chambers. 



At present 1 cannot give a. decision as to the exact significance 

 to the life of the sponge of the oxygen, which the living green 

 algae produce within its tissue in the light. It is possible that this 

 oxygen has a very great signiticance; so great, indeed, that the 

 katabolic phase of metabolism in a green sponge in light takes on 

 this account a quite different course — namely in giving a relatively 

 larger quantity of energy to the sponge — than in the sponge in 

 the dark. Some indications were found for this. 



Finally I came to the conclusion that direct transfer of assi- 

 milates (carbohydrates, fats, proteins) from the living green algae into 

 the sponge tissue does, most probably, not take place at all. 



If one now inquires what may really be the "symbiotic" relation 

 between sponge and green alga considered from the point of 

 view of its usefulness to the sponge, this question cannot be answered 

 very well before the above problem of the significance to the sponge 

 of the oxygen produced by the algae has come to solution : 



If the significance of the oxygen is in fact so great as was indicated 

 above, then, notwithstanding the fact that the sponge continually 

 destroys and digests the algae in great numbers and in spite of 

 all other phenomena which do not agree very well with symbiosis, 

 we are nevertheless obliged to conclude, that the relation between 



