66 



but 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. Such a sponge cul- 

 tivated in darkness behaved like type III. 



The results of our exjieriments may be resumed as folloivs: 

 1. Green S])ongillidae 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 Spongillidae 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 

 results were obtained by cultivating the sponges under such cir- 

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

 growth were almost etitirely excluded. Cotisequently , the facts stated 

 here must necessarily be explained by the two remaining factors: 

 that of multipdication 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 > mo (II) 



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



{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: 



