70 



(I) green sponge in light: 

 (II) green sponge transported into darkness: 



I 



(III) light-green sponge in darkness: 



(IV) colourless sponge in darkness 



é -|- r + mu := e -\- (/ -{- mo 



11 II V II V A 



i + r -\- mu < e + (/ + mo 

 II II II V V VA 

 i + r -f >nu <C e -\- g -\- mo 



II II II V V V 

 i + r + mu = e -\- g -\- mo ■ 



II II II II II II 

 i + 0+ 0=0 + ^ + mo 



II II II 



i = g -\- mo 



From this we see that, if in nature a sponge containing an 

 arbitrary number of green algae, so a more or less green sponge, 

 ivhich grew in light and kept up its colour, is transported into 

 darkness, it must unavoidably lose all its green algae and accord- 

 ingly become colourless itself, especially in consequence of a very 

 much decreased multiplication and a strongly increased mortality 

 of those algae in darkness. When all green algae have disap- 

 peared, the sponge is able only by continually imjwrting new ones 

 from outside to keep up a very small number of green algae in 

 its tissues, as these too continually disappear by dying (conf. Table 

 6 and p. 47, 3). 



B. Now the reverse. What will happen, when a sponge in 

 nature containing an arbitrary small number of green algae, 

 which grew in darkness and kept up its colour, is transported 

 into day-light ? In darkness the formula i + r -\- mu = e ~{- g -\- mo (I) 

 was binding for its green algae. Now, in light the multiplication 

 of the algae must become much more intensive, the mortality 

 much lower, the import remains the same, also the export (at 

 least in the beginning), while the factor of growth (in the be- 

 ginning) as well as the reduction (= 0) remain the same. The 

 original equation * + ?• + mu = e + g + mo passes into i + r -\- 



