1063 



probably very closely related lo Pleurococcus. For reproduction takes 

 place not at all by "freie Zellbildnng" (cell division preceded by 

 free nuclear condition), but by simple vegetative division of the 

 whole mother-cell. 



III. Generally speaking the spongillidae are green in the light 

 and colourless, i.e. cream-coloured in the dark (in twilight); whilst 

 green sponges generally become colourless in the dark, and colourless 

 ones green in the light. Lankester (I.e.) found that in colourless 

 sponges the otherwise green chlorophyll-corpuscles were colourless; 

 and he then concluded that these colourless corpuscles are either 

 directly transformed by the influence of sunlight into chlorophyll 

 granules or that during their development, by sunlight, instead of 

 yielding the colourless form they pass into the green type. In the 

 same way Brandt (I.e.) says, when speaking about these colourless 

 corpuscles: "eben so gut wie die Chlorophyllkörper von höheren 

 Pflanzen, können doch aber auch die Chlorophyllkörper von Algen 

 bei mangelhaftem Lichtzutriit blasser werden"; and elsewhere "dass 

 die Chlorophyllkörper der Zoochlorellen ihre grüne Farbe im Dun- 

 keln einblissen ist selbstverstandlich." Both authors, therefore, imagine 

 conformity of the behaviour in the dark of the chlorophyll-corpuscles 

 of spongillidae to that of the chloioplasts of higher plants, and so 

 they explain the above mentioned facts by analogy to the fact known 

 for angiospermae, for instance, that chlorophyll cannot be produced in 

 the dark. This I found to be quite inexact. Want of light is indeed 

 the cause why the colourless sponges remain colourless or the green 

 sponges become colourless in the dark, but for a wholly different 

 and much more complicate reason than Brandt and Lankester 

 think of; as will now be shown. 



I established that the isolated green symbiotic algae, cultivated in 

 water, can certainly produce chlorophyll in the dark; whilst I also 

 found, that these' green algae, when cultivated in the light and in 

 the dark, alike in poor and in rich organic feeding media, remain 

 alive and normal (gi-een) for months and multiply, but that 

 the isolated colourless algae under similar conditions sooner 

 or later disappear from the culture, and never pass into the 

 green form. It proved therefore quite impossible, that these green 

 sponge-algae should pass into colourless ones, and the colourless 

 into green ones by the combined influence of darkness or light 

 and some or other feeding medium, such as might perhaps have 

 been expected in analogy to the results obtained by Beyerinck, (I.e.), 



