95 



amocbocytes of green sponges lodge, besides tlieir nuineruus green 

 algae, mostly also one or more colourless algae free in their pro- 

 toplasm ; while, after what was said above, it stands to reason 

 that also the amoebocytes of colourless sponges contain colourless 

 algae free in their protoplasin. 



24-. In green and colourless sponges the amoebocytes appear to 

 lodge more colourless symbiotic algae than foreign enclosures 

 (unicellular algae, etc). The same thing counts for the whole 

 sponge-tissue. 



25. Particles, which have been taken up by amoebocytes, never 

 come immediately in a vacuole but remain free in the protoplasm ; 

 if a vacuole is formed around, this only happens lateron. 



26. From ïable 8 it appears, that in green sponges cultivated 

 in water from the conduit the number of colourless algae with 

 structure generally also increases in the light. 



Now that we have described in the above given 26 points the 

 chief facts, irhich bear upon the question aboiit the use of the 

 symbiotic association to the sponge^ we tvill now see, if all these 

 various data caii be united into one conception; in other ivords^ 

 if we can come to an answer to this question with the help of 

 these data. Probably one will suppose already oneself in which 

 direction the conclusion can be found, by the way in which now 

 the 26 points have been arranged. I must confess, however, that 

 this solution has troubled me a great deal; while on one point 

 it requires still further completion. 



As was mentioned under point 17 and 18, the fresh-water sponge 

 seems to digest free in nature only little nutrition (symbiotic 

 algae and other food particles) by means of food-vacuoles. So 

 the sponge must evidently supply its food ii; another way. Several 

 ways are imaginable: 



First the possibility, that the sponge lives of organic materials 

 in solution, present in the lake water. I ani not going to treat 



