112 



sponge and greeri alga is, considered from the point of view of the 

 use to the sponge, we cannot verg well answer that qnestion, hefore 

 the prohlem, mentioned ahove, ahout the significmice for the sponge 

 of the O., secreted hg the green alga i?i the light, has come to 

 solutiofi : 



a. If the significance of that O., is in f act so important, as tvas 

 fhought possihle above, we must conclude — notwithstanding the 

 fact, that the sponge continnallg destroys and digests numbers of 

 algae, and notwithstanding all otlier phenomena, tvhich do not seem 

 to go together with a sgmbiosis — that the reJdtion of sponge and 

 green alga, considered from the point of view of the use to the 

 sponge, is in fact a sgmbiosis, though this sgmbiosis is bg no 

 nieans so complete as that of the Lichens. 



b. If, on the contrary, the significance of the 0.^ secreted bg the 

 alga is onlg of little importance, ive can conclude — whatever 

 mag be the real cause of the dying of the algae in the sponge 

 tissue, wether it be the want of food of the spo7ige or {and) the 

 „p)oisoning^' of the cdgae bg products of metabolism of the sponge — 

 we must conclude that, practically spoken, that so colled symbiotic 

 relation of spo?ige and alga is in fact nothing hut simply aprocess 

 of nutrition of the sponge, or, if gou like, a verg frst transition 

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

 counts for a sponge in darhness. 



For ive could state the folio witig : 



The sponge continuallg imports green algae from. the surrounding 

 water into its amoebocytes {p. 50), where those algae then — it should 

 be explicitly mentioned — are killed and digested {p. 111) by the 

 sponge o?ily for a part, when circumstances are favourable; 

 tvhile the rest of the algae can live on, photosynthesise and mul- 

 tip)ly {and will give their f\, produced in light, to the sponge 

 tissues {p. 93) — the onlg argument one can mention iri favour 

 of the conception of symbiosis !). This favourable case is only realized 

 in spo7iges growing in light {p. 70^72) — for in light i y mo ') — 



1) This foUows from p. 70 IV, p. 51, and p. 60 — 01, 59. In darkness i — mo; so in 

 light i > mo. 



