62 



beginning and at the end of the experiments), the above obtained 

 result (p. 60) — that more algae die in darkness than in light — 

 remains valid ; then there are even some more experiments 

 leading to the same result: n". (246, 248) — (255, 256), 339, 

 840, 367, 368, 369, 370, 374, 378—377. Moreover, the exact- 

 ness of this result — not only for a same strong concentration 

 of the green algae, but also for a same weak one — also follows 

 very clearly from the last two argumentations. 



Finally I should mention that we have realized the fact in 

 these cultures of green sponges in aquaria in darkness, that of 

 all 6 factors, normally ruling the number of algae in sponge 

 tissue, only the factor of dying has (practically) remained. 



Afterwards I will treat the cause of the dying of the algae 

 in sponge tissue, when speaking about the symbiotic relation of 

 sponge and alga. 



Having studied the 6 factors ruling the number of symbiotic 

 algae in sponge tissue separately, we are now going to examine, 

 if some combinations of those factors can be realized. We will not 

 take into consideration the uncertain factor of export, the ab- 

 normal one of reduction and the but slowly working factor of 

 growth, in order to combine the 3 principal factors of import, of 

 multiplication and of dying : 

 I. Import + multiplication can not be realized, of course. 

 II. Import + dying is realized, together with growth, in nature 

 in colourless sponges in darkness. See Table 6. 

 III. Import + multiplication + dying is realized, together with 

 growth, in nature in green sponges in light. See also Table 6. 

 lY. Multiplication + dying can be realized by cultivating green 

 and colourless sponges in flowing water from the conduit in light 

 and in darkness for not too long a time; in this way the factors 

 of import, (export,) reduction and of growth will be excluded as 

 much as possible. These experiments are very important ! For we 

 will succeed in this way to transmute green sponges into colourless 



