58 



of rapidity, with which the colourless stages are goue through, 

 as caused by : a. a changing influence produced by the green 

 algae on the sponge tissue (production of 0.^ and assimilates in 

 light, but not in darkness), h. some other influence independent 

 from those green algae. I will treat both possibilities in con- 

 nection with my experiments. In order to get a pure result, the 

 factors of import, (export), growth, reduction and of dying should 

 be excluded as much as possible in these experiments; which 

 may be obtained by cultivating colourless sponges (so sponges 

 containing a small number of green and a large number of colour- 

 less algae) in flowing water from the conduit, and to continue 

 the experiments for not too long a time. These experiments 

 belong to a large series of similar ones, made for different 

 purposes (Table 8). My material consisted in Spongillae and 

 Ephydatiae; generally of each sponge a piece was cultivated in 

 light and another piece under the same conditions in darkness. 

 In the beginning of the experiment both pieces of each pair 

 possessed an almost equally small quantity of green and of colourless 

 algae with structure, and an almost equally large quantity of 

 colourless ones without structure. Table 8, n°. 336, 365 I, 365 II, 

 375, 376 give an answer to the possibility mentioned sub h. For 

 at the end of these experiments: 1. the quantity of green algae 

 proves to be just as small as at the beginning, and therefore to 

 have been of no influence, 2. the large quantity of colourless algae 

 without structure in each sponge piece in light proves just as much 

 increased, decreased or remained equal during the same time as 

 in the partner sponge piece in darkness; pi'oof^ that in sponge 

 tissue^ when the number of green algae is small, the stage of co- 

 lourless alga without structure is imssed in light just as quicMg 

 as in darkness. Table 8, n«. 263, 264, 298, 299, 337, 338, 341— 

 342, 347 — 346 give an answer to the question mentioned sub a. 

 For at the end of these experiments: 1. the quantity of green 

 algae proves to have increased rather much in light, therefore 

 perhaps of much influence, 2. the Jarge quantity of colourless algae 

 without structure in each sponge piece in light proves to have 

 changed just as much, or more increased in the same time than 



