1064 



Artari '), Grintzesco *), Radais ') with various otiier algae. I 

 established, however, that the green symbiotic algae can become 

 colourless only by dying; in order to pass subsequentlj- and gradually 

 from colourless algae with well-defined internal structure through 

 various "stages of dissolution" (colourless ones with a shadowy 

 internal structure, colourless ones without internal structure, and 

 shades of colourless alga«) and finally to disappear from the sponge- 

 tissue or from the culture. 



After I had stated this, I made analyses of the intrinsic amount 

 of the various (green and colourless) stages of the symbiotic algae 

 in the tissues of a large number of green spongillidae, from the 

 light and of colourless ones ^ from the dark. The results are too 

 numerous to be given here in extenso; briefly, it may be said, 

 that a green sponge in light contains an excess of green living 

 algae and a smaller number of colourless dead algae; on the other 

 hand a colourless sponge in the dark contains an excess of colour- 

 less dead ones and a smaller number of green living algae. 



I then studied the factoi'S, which regulate the number of symbiotic 

 algae in the sponge-l issues, each one separately (per unit of time 

 and per unit of volume of the sponge). These factors are 6 in 

 number: 1^'. The import {i) of algae from the water into the 

 sponge, a powerful factor in nature and as active in light as in 

 darkness. 2"''. The export {e) of the algae from the sponge into the 

 surrounding water, an uncertain, but probably not important factor. 

 3"^. The reduction {r) of the sponge-tissue to a smaller volume, a 

 factor which in nature only occurs in autumn and then might cause 

 an increased concentration of the algae in the tissue. 4''\ The growth 

 {g) of the sponge-tissue, which in the long run must lower the 

 concentration of the algae and which in green sponges in the 

 light is more vigorous than in colourless ones in the dark. 

 5^'\ The intensity of multiplication {inu) of the algae, which in sponges 

 at equal concentration of the algae is much greater in light than in 

 darkness, in light at high concentration greater than at low 

 concentration, but in the dark in both cases pretty well zero. 

 6''\ The mortality {mo) of the algae, which in sponges at equal 

 concentration is much greater in the dark than in light, and at low 

 concentration is in the dark less than, but in light as great as that 

 at high concentration. 



With the aid of these data concerning the Q factors we can now 



1) Berichte Dt. Botan. Ges., 1902. 



2) Revue génér. de Botanique, T. 15, 1903. 

 8) C. R. Acad. d. Sc. Paris, T. 130, 1900. 



