59 



in the partner sponge piece in darkness; pyotjf\ fJiut in spomje 

 tissue^ when the nwnher of f/reen algae is important^ the stage of 

 colourless alga ivitJiout structure is passed in light eifher just as 

 quicldy or less quickly than in darkness^ hut hy no means more 

 quickly. Besides, this is logical (cf. chapt. VIII). Something 

 the like will evidently be the case, when one compares a sponge 

 in light containing many green algae and one containing hut a 

 few; for the latter will bohave almost like a sponge in darkness. 



Now we proceed to the comparison of the mortality of the 

 green algae in sponge tissue in light and in darkness. Are there 

 more, or less algae dying in a sponge in light than in a sponge 

 in darkness? 



From the results obtained through analyzing the niimbcr of 

 algae in sponge tissue (Table 6, pag. 46 — 48) we may immedia- 

 tely answer this question, if we consider that 1. in colourless 

 sponges in darkness the import is the only factor keeping up the 

 number of green algae (pag. 51), and that 2. the import is 

 equally active in green sponges in light as in colourless ones in 

 darkness (pag. 51). We may thus conclude that^ aUhouglt the 

 colourless sponge i?i darkness possesses miich less green algae than 

 the green sp)onge in light (pag. 47^ 8), still more green algae die 

 in the colourless spoyige in darkness — as the intensity of dying (the 

 number of colourless algae with structure) as well as the total 

 amount of dead algae (the number of colourless ones without 

 structure) is at its largest in the colourless sponge (pag. 48, 9). 

 Consequently, much more specimina of a same quantity of green 

 algae die in a colourless sponge in darkness than in a green 

 one in light. 



As to this fact, one might object tjiat it might be possible 

 that a sponge (in light, for instance) regularly wants — it may 

 contain many or but a few green algae — a same quantity of these 

 algae to feed upon; that therefore it would not be of any use to 

 calculate the mortality per same number of green algae, as then 

 one would find, of course, a large relative amount of dead algae 

 in a colourless sponge, even if it did not grow in darkness. 

 ïhis reasoning might be exact, certainly (see below); but in any 



