66 



bilt in 2 specimina the number of these algae increased, while 

 4 other ones became greener in the beginning in order to lose 

 all colour afterwards. So Ephydatia in darkness proves to behave 

 like Spongilla. 



C. Finally 8 sponges of unknown genus, cultivated in light; 

 4 behaved like type I and 4 like ^type II. Siich a sponge cul- 

 tivated in darkness behaved like type UI. 



The residfs of our experiments may be resumed as foUoivs: 

 1. Green Sjmïigillidae remain green in light. 2. Colourless Spongil- 

 lidae remain colourless in darkness. 3. Colourless Spongillidae be- 

 come green in light. 4. Green Spongillidae become colourless in 

 darkness. 5. When Spoyigillidae are cultivated in light^ the increase 

 of the green algae surpasses the decrease. 6. When Spongillidae 

 are cultivated in darkness, the decrease of the green algae sur- 

 passes the increase. I want to point out emphatically that these 

 residts were obtained by cultivating the sponges under such cir- 

 cunistances, that the factors of import, export, reduction and of 

 growth were almost entirely excluded. Consequently , the facts stated 

 here must . necessarily be explained by the two remaining factors : 

 that of multiplication and that of mortality. Therefore the results, 

 given in these factors, run in the following way : 



1, 2 for green sponges in light and colourless ones in darkness : mu = mo (I) 



3, 5 for light-green and colourless sponges in light : mu > 7no (II) 



4, 6 for green and light-green sponges in darkness: mu<imo(in.) 



(mu = factor of multiplication, mo =^ that of mortality) 



Proceeding from formula I, we will now prove the exactness 

 of the other formulae by means of the above obtained data 

 (p. 55 — 56, 60, 61) concerning the factors of multiplication and 

 mortality. This is quite simple. We proceed from a green sponge 

 grown in an aquarium in light; for this formula (I) mu = mo is 

 binding. What happens, when we transfer this sponge into an 

 aquarium in darkness? Then this green sponge must pass into a 

 colourless one — according to our data. We may symbolize this 

 transition in this way: 



