41 



normal (green, for instance) and alive for months, and multiply 

 by normally green descendants. 



2. In general the number of isolated colourless symbiotic 

 algae (with structure) does not increase in these cultures, but 

 decreases; they disappear from the culture. 



So the green symbiotic algae of the sponges belong to type A, 

 B, III, to the same type as the symbiotic algae of Xanthoria. 



Next I wanted to examine (pag. 39) if the colurless form of 

 the symbiotic algae may pass into the green one by a certain 

 combination of light (or darkness) and feeding milieu. I cultiva- 

 ted therefore the isolated colourless algae in light and in darkness 

 in the same feeding solutions, as the green ones were cultivated 

 in. I refer to Table 4 C, D. The result was : 



The isolated colourless symbiotic algae of the SpongilUdae (n.b. 

 those with structure), whether cultivated in light or in darkness 

 in poor or in rich organic feeding solutions, even in liquid pressed 

 from a sponge, disappear from the culture after some time] they 

 never pass into the green form. 



We may now conclude: It is impossible, that the green sym- 

 biotic algae pass into the colourless ones, nor can the colourless 

 algcce pass into the green ones, by the combined inflnence o f darkness 

 or light and a certain feeding milieu — at least not in those cases, 

 which regard the condition of the sponge. This also proceeds from 

 the following facts : 



As I stated above, green sponges generally occur in light and 

 colourless ones in darkness or twilight. In nature however — as 

 exception to the rule, but by no means very seldom — colourless 

 sponges also occur in light and — rather seldom — green ones in 

 twilight. Sometimes one may even find, close together, some green 

 and colourless sponges in bright daylight, or in twilight. It goes 

 without saying that — as in each of these two groups of sponges 

 (that in light and that in darkness) the algae live under the same 

 conditions as to light and food — one may not attribute the fact 

 of the majority of the algae being green or colourless in one case 

 or in the other to the combined influence of those two factors. 



