178 



10. The isolated green „symbiotic"' algae of the Spongillidae, 

 in water, can produce chlorophyll in darkness (p. 37, Table 4 B). 

 Those green algae also, whether cultivated in light or in dark- 

 ness in poor or in rich organic feeding media, remain normal 

 (green, for instance) and alive for months, and multiply ; while 

 the isolated colourless algae under similar conditions disappear 

 from the culture and never pass into the green form (p. 38 — 41, 

 Table 4). It proves, therefore, quite impossible that the green 

 algae pass into the colourless ones and that the colourless algae 

 pass into the green ones, by the combined influence of darkness 

 or light and a certain feeding milieu (p. 41). 



11. The green „symbiotic" algae, whether isolated or in the tissues 

 of the Spongillidae, become colourless exclusively by dying, in order 

 to gradually pass from colourless algae with clear structure into 

 the successive stages of „solution", colourless algae with shade 

 of structure, colourless ones without structure, vague shades of 

 colourless ones, and to finally disappear (p. 42 — 45, Table 5, Fig. 

 35—37). 



12. Analyses were made of the intrinsic amount of the various 

 green and colourless stages of the „symbiotic" algae in the tis- 

 sues of a large number of green Spongillidae from light and of 

 colourless ones from darkness, and such in tissues in different 

 stages of development (Table 6). The results are to numerous to 

 be repeated here; they are mentioned on p. 46 — 48, point 1 — 11. 

 In short we can say, that a green sponge in light contains an 

 excess of green living algae and a smaller number of colourless 

 dead ones; a colourless sponge in darkness, on the contrary, an 

 èxcess of colourless dead algae and a smaller number of green 

 living ones (p. 48). 



13. The factors, ruling the number of the „symbiotic" algae 

 in the sponge tussues, were studied separately (per unit of time 

 and per unit of sponge-volume). These factors are 6 in number: 



a. The import (/) of the algae from the surrounding water 

 into the sponge tissue, a powerful and continually acting 

 factor in nature and equally active in light as in darkness 

 (p. 49—51, Table 7). , 



