83 



while those for the weak concentrations (w. — m. and w. — w.) 

 are lower in sponge tissue than in water. But, of course, the 

 correspondence of the intensities for the concentrations s. — s. and 

 m. — s. is the most decisive. So we are justified in concluding 

 that the symbiotic algae multiply in light in equal, strong con- 

 centration mthin the tissue of the sponge about just as quickly 

 as in tvater; but in equal, weak concentration in the sponge less 

 quickly tha?i m water. From this we may also, deduce (p. 77) 

 that the feeding milieu for the alga is in fact not more favour- 

 able in the sponge than in the water, but about just as favourable 

 or even less favourable. That it is not more favourable, also very 

 clearly shows from the fact, that the algae multiply in darkness 

 less quickly within the sponge tissue than in water (Table 10, 

 cnf. Table 6, col. 2 and Table 4 B, col. 4). 



It is a matter of course that the above proved fact about the 

 protection, which a sponge in light gives to its algae, does not 

 lose anything of its validity, now that we have shown that the 

 greater intensity of multiplication in water, which occurs in 

 these experiments, is not^^plained by the milieu but^ simply by 

 the concentration-differences of the algae (see note p. 78). 



But what about that protection (p. 78) in darkness? It appears 

 from Table 10, col. 3, and also by comparing Table 4 B and 8 

 that — contrary to the result in light — the algae in darkness 

 are in much less favourable conditions in the sponge than in the 

 water ; in the sponge all algae are destroyed within short (p. 70). 



As final conclusion ') we may give this one: In darkness the 



1) In fact we should have stated this not only by comparing the behaviour of algae 

 when cultivated in water from the conduit and in sponges in water from the conduit, 

 but also by comparing their behaviour in lake water and in sponges in lake water. 

 This, however, is impossible, as we can cultivate sponges only in pure streaming water 

 (p. 9), and as, moreover, the factor of import cannot be excluded in experiments in 

 lake water (p. 11). But in any case we know that the feeding milieu is less favourable 

 to the algae in lake water than in that from conduit (p. 82), and that in light the 

 algae are also in less favourable total-conditions in lake water (than in that from 

 conduit) (Table 10, col. 3). From which perhaps might follow that in light the de- 

 struction of the algae in lake water is about just as large as in that from conduit, 

 at least is not weaker. 



