wants more food than the green — once more, this cannot have 

 its cause directly in the algal products of photosynthesis — but 

 in what then? Perhaps the following solution holds good: 



In connection with what was mentioned in point 16 (p. 93), 

 one must admit, that the green sponge in the light disposes of a 

 very considerable abundance of 0.^ in its tissues, which the (colour- 

 less) sponge in the dark cannot have, of course. It is now 

 acknowledged in general physiology, that the katabolic phase of 

 metabolism has quite another course in lack of 0.^ than in abun- 

 dance ; in lack of 0^ a much more largely, but much less deeply 

 extending break -down of body-materials (proteins, carbohydrates), 

 takes place than with sufficient 0.^ — Yerworn (58), Hermann 

 (28), Hammarsten (26), Biedermann (6), De Vries (63) — ; 

 indeed, in lack of 0.^ much more material is required for obtaining 

 a certain quantity of energy, as the organism for source of energy 

 is then chiefly dependent on not oxidative splittings which procure 

 but little energy, while then, also by the faulty oxidation, a great 

 deal of the chemical energy of the splitting-products is lost for 

 the organism. In this way one would be inclined to explain the 

 fact, that the colourless Spongilla in darkness wants more food 

 than the green one in the light '). For the present this is but 

 a suggestion, to which I shall return however later on. 



Now that we have seen that the freshwater sponges for a great 

 deal, perhaps even chiefly, find their food in the symbiotic algae, 

 which continually die and are digested and dissolved free in the 

 protoplasm of their amoebocytes, the connection, which there is 

 according to point 7 (p. 89) between the number of oildroplets 

 in the amoebocytes (point 3) on the one side and the number of 

 dead (colourless) algae in the sponge tissue on the other side, 

 may be explained quite simply. For the sponge tissue disposes 

 of a lipase (point 8), and in point 1, 2 (p. 84) we found 

 an always decreasing percent of algae with an oildroplet. 



1) That this seemed not to be the case. with Ephydatia, might be explained from the 

 fact, that the colourless specimina I examined, which contain always some green algae, 

 were partly originating from the light. 



