44 



III. On pag. 41, treating the cultures of isolated colourless 

 algae, we concluded that these algae (n.b. those with structure) 

 always disappeared from the cultures, and never passed into 

 the green ones. The same proves to be the case (Table 4) for 

 the isolated colourless algae without structure. Which was already 

 self-evident. 



We have proved now, that the green sponge algae may change 

 into the colourless ones by dying. We shall have proved incon- 

 testably, that the green symbiotic algae within the sponge tissues 

 become colourless exclusively by dying (in order to disap- 

 pear afterwards), only when we have shown that all colourless 

 algae present in these tissues are really dying. The following 

 are the proofs : 



TV. The general rule given under III ; while, on the contrary, 

 the green algae remain alive for months. 



Y. When a sponge dies, its colourless algae do not remain 

 intact — as the green ones (p. 28) — but they disappear. 



YI. Colourless stages of division of symbiotic algae are but 

 seldom to be found in sponges — on the contrary several green 

 ones (Table 6) — ; therefore the former must probably be explained 

 as having been originally green. 



YII. As known, living protoplasm is generally not stained, 

 or less quickly stained than dead one. By means of this fact I 

 could definitively decide whether the colourless algae were alive 

 or not. I therefore made ravel preparations of living, green and 

 colourless sponges, and added equal quantities of a solution of 

 eosine or methylene-blue in water, with the following results: 



1. Gree?i Spongilla material containing numerous green symbiotic 

 algae, a few colourless ones with structure, and rather numerous 

 colourless ones without structure. 



A. In eosine. After 25 hours the numerous green algae have 

 as a rule not been coloured red, only very seldom one meets 

 with a green specimen with red tint. Colourless algae are but 

 very seldom to be found, almost all of them are red : the few 

 with structure - they have n o green chloroplast ! — as well 

 as the rather numerous ones without structure. 



