204 



Table 8. CuHures of' green and colourless apongillidae in light or 

 in darkness in^aquaria filled with flowing ivater from the conduit; 

 'While the colour of the sponges and the number of the various green 

 and colourless clilorophyll corjniscles in the tissues changes or remains 

 constant. 



Generally of each sponge some pieces were cultivated in light and 

 some other ones under equal circumstances in darkness; such pieces 

 of one sponge are indicated in the tables with one n", adding 1. or d., 

 event. I and II, to it. These cultures, of course, may be compared 

 directly. The colour, and generally also the number of the various 

 chlorophyll corpuscles in the tissues of each sponge (- piece) was exactly 

 examined (pag. 13^15) at the beginning as well as at the end of the 

 experiment. Mostly the material of the branch-tops was well discerned 

 from that of tlie branch-bases (see Table 6 A). 



The cultures took place, as mentioned, in aquaria with flowing 

 water from the conduit or sometimes in glass vessels witli 3 L. of the 

 same (but not flowing) water. As for the arrangement, see pag. 8 — 9. 

 The cultures were kept till the sponges began to die or to reduce 

 their tissue; Spongillae usually after about 1 month, Ephydatiae after 

 about 2 months. In this way the factors of import, (export), reduction 

 and growth (p. 49 — 53) were excluded as much as possible in these 

 experiments; while as only active factors remained multiplication and 

 mortality (pag. 54 — 62). 



That import was excluded follows from the fact that the sponges 

 were cultivated in water from the conduit. The export is, as stated 

 above, an uncertain but probably not important factor. The reduction, 

 as mentioned, was excluded by putting a stop to the experiments, as 

 soon as it appeared; while, moreover, a continual vigorous circulation 

 of fresh water through the aquaria tried to limit its troubling con- 

 sequences as much as possible (p. 53). Had these measures been not 

 entirely sufficient (which cannot be decided), one may consider, how- 

 ever, safely that the reduction will have equally influenced all expe- 

 riments of one series. The factor of growth, of course, can never be 

 entirely excluded; but in these experiments it was generally but very 

 weak only (p. 53). 



In the table is indicated : a. Tlie n'' of each experiment, h. The 

 species of the sponge piece (s. = Spongilla; e. = Ephydatia). c. Whe- 

 ther the piece was cultivated in an aquarium (a.) or in a glass vessel 

 (v.). d. The date of the examination, e. Whether the examined mate- 

 rial was taken from a branch-top (t.) or from a branch-base (b.). 

 f. Wheter the sponge, at the moment of examination, was in good 

 condition (g.) — ■ showing no or but few reduction — , or that more 



