182 



a. If the significance of that O.^ is in fact so important, as 

 was thought possible above, we must conclude — notwith- 

 standing the fact, that the sponge continually destroys and 

 digests numbers of algae, and notwithstanding all other 

 phenomena, which do not seem to go together with a sym- 

 biosis — that the relation of sponge and green alga, con- 

 sidered from the point of view of the use to the sponge, is 

 in fact a symbiosis, though this symbiosis is by no means 

 so complete as that of the Lichens. 

 h. If, on the contrary, the significance of the O^ secreted by 

 the alga is only of little importance, we can conclude — 

 whatever may be the real cause of the dying of the algae 

 in the sponge tissue, whether it be the want of food of the 

 sponge or (and) the „poisoning" of the algae by products 

 of metabolism of the sponge — we must conclude that, 

 practically spoken, that so called symbiotic relation of sponge 

 and alga is in fact nothing but simply a process of nutrition 

 of the sponge, or, if you like, a very first transition of a 

 process of nutrition into a symbiosis. At any rate this always 

 counts for a sponge in darkness. 

 For we could state the following: 



The sponge continually imports green algae from the sur- 

 rounding water into its amoebocytes (p. 50), where those algae 

 then — it should be explicitly mentioned — are killed and 

 digested (p. Ill) by the sponge only for a part, when circum- 

 stances are favourable, while the rest of the algae can live on, 

 photosynthesise and multiply (and will give their O^, produced 

 in light, to the sponge tissues (p. 93) — the only argument one 

 can mention in favour of the conception of symbiosis!). This 

 favourable case is only realized in sponges growing in light 

 (p. 70—72), and then not even always (p. 41, 75—76). If, however, 

 the circumstances are somewhat less favourable — as is the rule 

 in sponges in darkness (p. 69 — 70) and as sometimes happens 

 also in those in light (p. 41, 75—76) — , then all imported algae 

 (and all that might be present already) are continually and un- 

 avoidably destroyed and digested by the sponge (p. 111). 



