80 



So here we have siich an (apparently) paradoxal phenomenon, 

 as treated above in consequence of the comparison between multi- 

 plication-intensity and total increase of the algal-culture in a 

 sponge and in water; indeed, here too we found a smaller total 

 increase with a larger multiplication-intensity of the symbiotic 

 algae (in water). 



So one proof more, that this intensity of miiltiplication 

 and this total increase are independent factors ; while, what 

 we treated just now, gives even more support to the above 

 mentioned opinion, that the protection of the symbiotic algae by 

 the sponge is, among others, also meant against diatoms and 

 ordinary algae. 



It stands to reason, that this protection must now not be taken, 

 as if there are no algae destroyed in the sponge itself. Of course 

 this does take place, as we saw, eg. on p. 46 — 48. 



On p. 78 we saw that in the cultures of Table 10 the intensity 

 of multiplication of the green algae in light was generally much 

 higher in water than in the sponge tissue. I have purposely 

 omitted till now treating the cause of it, to evade unnecessarily 

 complicating the question we were about. 



Yery likely that cause is not to be found in the milieu, in the 

 sponge or the water, but in the concentration-diiïerence of the 

 algae themselves (see p. 55). It might seem to be very difficult, 

 almost impossible, to directly compare the concentration of the 

 algae in water and in the sponge tissue somewhat accurately. 

 Nevertheless, I believe to have succeeded rather well ; and I so 

 came to the conclusion that in fact in the light, in an equal, 

 strong concentration of the green symbiotic algae, their intensity 

 of multiplication in water and that in the sponge are probably 

 the same. 



In the first place we see that in Table 10 there are also cases 

 to be found in which the intensity of multiplication in the sponge 

 is just as high as that in water, or just the reverse, that the 

 intensity in water diminishes down to that in the sponge. The 

 first regards sponges with weak concentration of the green algae 



