1062 



It was therefore very desirable definitely to settle this point of 

 difference, first of all, however, I had to complete the investigations 

 of Brandt and of Lankester, who had concerned themselves with the 

 identity in a physical sense of the chlorophyll in freshwater sponges 

 with that in plants, but had left the physiological identity out of 

 consideration, I have been able to prove this latter identity 

 by showing experimentally, that the green chlorophyll-corpuscles of 

 the sponges in light produce 0, and assimilates (oil), but not in the 

 dark. And with regard to the controversy as to the origin of this 

 chlorophyll, I have been able to prove by stronger and more 

 convincing arguments than Brandt furnishes, that his conclusion 

 was indeed right : The chlorophyll-corpuscles in the sponges are 

 composed of protoplasm and chloroplast (also established by Brandt 

 and Lankesterj ; they perhaps contain a nucleus (which Brandt 

 says he was able to show positively, whilst Lankester denies its 

 existence ; I do not consider Brandt's proof to be decisive) ; they are 

 surrounded by a cell-wall, which I was able to make visible by means 

 of plasmolysis (Brandt could not show it with certainty) ; in cultures 

 the green chlorophyll-coi-jxiscles, when separated from the sponge-tissue, 

 remain normal and alive for 6 months and even longer, and 

 multiply vigorously (Brandt mentions only a survival for 3 — 4 weeks, 

 whilst their niultiplicalion could not be established) ; the green chloro- 

 phyll-corpuscles of the sponges occur also free in nature, where they 

 also multiply (not observed by Brandt); finally the fact, that colourless 

 sponges can be transmuted permanently into the green form by infec- 

 tion with isolated green chlorophyll-corpuscles (not demonstrated by 

 Brandt either ; he only mentions — although with incomplete proof — 

 a case of "grafting" the chlorophyll-corpuscles from spongilla on a 

 stentor). These results therefore prove conclusively that the chlorophyll- 

 corpuscles of the fresh-water sponges are algae associated to the 

 sponge in "symbiosis". 



II. The investigators who hold Brandt's view all agree, that this 

 symbiotic alga belongs to the genus Clilorella, e.g. Beyerinck ^), 

 Oltmanns ^), WiLLE '). The mode of reproduction of these algae, 

 which I have been able to determine, has however shown me, that . 

 in the case of the sponges investigated here, we are by no means 

 dealing with a member of the genus Chorella, but with" a form 



1) Botanische Zeitung, 1890. 



') Morphologie und Biologie der Algen, 1904 — 05. 



3) In Engler und Praktl: Natürl. Pflanzenfamilien. Nachtrage zu 1^, 1911. 



