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less ones in darkness : 1. the mtensity of dijing of the green algae 

 remahis constant in all stages of development of the sponge tissue^ 

 showing however a considerable decrease in the gemmule-stage; 2. 

 the total amount of dead algae increases (in the unit of sponge 

 volume) during the development of the tissues, which is of course 

 a matter of fact. Nevertheless, it is important to see that the 

 latter shows from the analyses ; for it proves that these colourless 

 algae ivithout structure must hold in the tissues for rather a long 

 time. Is is even probable, that in full-grown tissue (at least in 

 the beginning) the same colourless algae without structure would 

 still be present, which were already there at the time the tissue 

 was young and growing; for their continually increasing number 

 can not be explained in another way (as the intensity of dying is 

 constant, and one should admit also that the number of dead algae, 

 passed at the same time from colourless ones with into colour- 

 less ones without structure, will also disappear at the same time 

 from this last stage). That the total amount of dead algae should 

 considerahly decrease during or after the gemmule stage is quite 

 conceivable, for then the intensity of dying proved much smaller, 

 while on the other hand colourless algae are continually dis- 

 appearing. 



Next we want to compare the mortality of the green algae 

 in sponge tissue in light and in darkness. For that purpose we 

 can make use of both groups of colourless algae mentioned here. 

 First we should ask however, if in the dying of the green algae 

 within a sponge the stage of colourless one with, as well as that 

 of colourless one without structure is passed in light just as 

 quickly as in darkness. One might answer that this question does 

 not come into consideration, as we concluded above: 1. that in 

 both cases the first stage is passed so quickly, that we may con- 

 sider it to be a measure of the intensity of dying during a short 

 period, and 2. that in both cases the algae can not possibly dis- 

 appear from the second stage before the sponge tissue is full-grown. 

 This is exact. Yet I shall also answer the question experimentally, 

 at least as far as the second stage is concerned. 



When asking this question, one thinks of a possible difference 



