opinion is almost generally acknowledged — eg. by Beijerinck (4) 

 1890, Delage (16) 1899, IIertwig (29) 1903, Oltmanns (47) 

 1905, Weltner (68) 1907 and Biedermann (6) 1911 — ; Sollas (53) 

 1906 only — and apparently Minchin (45) 1900 too — holds 

 the view of Lankester, though in a note he indicates the pos- 

 sibility of the chlorophyll corpuscles being algae. I will show by 

 decisive proofs that Brandt was right (see Summary, point 1 — 5). 



2. The investigators, who agree with Brandt, unanimously de- 

 clare that the symbiotic alga of the Spongillidae belongs to the 

 genus Chlorella — eg. Beijerinck (1. c.), Oltmanns (l.c), Schenck 

 (56) 1908, Wille (69) 1911 — . But having examined the mode 

 of reproduction of those algae, I have been able to state 'that, at 

 least in my sponges, we do not meet with a member of the genus 

 Chlorella at all, but with a forni probably closely related to the 

 genus Pleurococcus (see Summary, point 6). 



3. By lack of sufficiënt daylight green fresh-water sponges 

 become colourless, viz. creamy-white, and colourless sponges 

 remain colourless. In such sponges Lankester (1. c.) found the 

 chlorophyll corpuscles, which used to be green, now colourless; 

 and he concludes, that these colourless forms may either pass 

 directly into (green) chlorophyll corpuscles by the action of sun- 

 light, or that during their development, by sunlight, in stead of 

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

 the same way Brandt (1. c.) says, wlien speaking about these 

 colourless corpuscles: „eben so gut wie die Chlorophyllkörper von 

 höheren Pflanzen, können doch aber auch die Chlorophyllkörper 

 von Algen bei mangelhaftem Lichtzutritt blasser werden" ; and 

 elsewhere: „dass die Chlorophyllkörper der Zoochlorellen ihre 

 grüue Farbe im Dunkeln einbüssen, ist selbstversttindlich". So 

 both authors suppose conformity of the behaviour in darkness 

 of the chloroplasts of the higher plants and of the chlorophyll 

 corpuscles of the Spongillidae ; and so they explain the fact 

 mentioned above, viz. that in darkness green sponges grow colour- 

 less and colourless ones remain colourless, by analogy to the fact 

 known from the Angiospermae : that chlorophyll can not be pro- 

 duced in darkness. This, now, proved to me quite inexact. The 



