61 



without structure proves in all these cases, that also here more 

 algae dicd in darkness than in light). 



I want to point out emphatically that we got tliis result by 

 means of experiments in which the spongés in light contained a 

 large quantity of green algae. We therefore know (pag. 59) 

 that in these experiments the stage of colourless alga without 

 structure can not have been passed more quickly in the sponges 

 in light than in those in darkness, but that it has been passed 

 just as quickly^ or even less quickly in light. When we suppose — 

 to get a pure comparison — this stage to have been passed just 

 as quickly in both cases, the above obtained result must be 

 binding, perhaps even a fortiori. 



One should also examine, if there is any difference in the in- 

 tensity of dying of the green algae in the tissue of a sponge 

 with a strong and in that of a sponge with a weak concentra- 

 tion of green algae. To answer this question we may mutually 

 compare the number of colourless algae with structure in green 

 and in light-green sponges, after these sponges have been culti- 

 vated for some time in water from the conduit, in light or 

 in darkness (Table 8). At first after culture in light. We find 

 this number in 27 green sponges : 1 II -|- 2 III + 7IV4-10V4- 

 4 VI + 3 VII and in 18 light-green (or colourless) ones : 1 I + 

 1 II + 2 III + 3 IV + 4 V + 4 VI + 3 VII. So it follows that in 

 light the intensity of dying of the green algae in sponge tissue in 

 a weak co7icentration is almost just as large as in a strong con- 

 centration of the algae (calculated j;er unit of sponge volume). 

 Then the same for sponges cultivated in darkness. In 8 green 

 sponges the number of colourless algae with structure proves to 

 be : 1 II + 1 III + 1 V + 3 VI + 2 VII, and in 37 light-green (or 

 colourless) ones : 2 I + 5 III + 8 IV + 4 V + 10 VI + 8 VII. Con- 

 sequently, in darkness the intensity of dying of the green algae 

 in sponge tissue in a weak concentration is somewhat smaller than 

 in a strong concentration of the algae (calculated per unit of 

 sponge volume). 



When we consider both these facts in all experiments of Table 

 8 (with respect to the concentration of the green algae in the 



