9 



by an open wiïidow. The aquaria contained water froiii tin; con- 

 duit, which was continually flowing in; as I may conclude from 

 my experiments , the water was entirely renewed in this way 

 in 5 — 10 hours. Plants, nor any nutriment for the sponges were 

 ever added — pure, streaming water proved to be best. In the 

 aquaria the sponges were in (tempered) daylight, not too many 

 together, in their natural attitude lying on wire-gauze, 10 — 20 

 centimeters from the bottom and 15 — 20 centimeters from the 

 surface of the water; in this way they were safe from the in- 

 fluence of anything that might sink to the bottom. The aquaria 

 were cleaned once in 1 — 2 months. For culture of sponges in 

 darkness aquaria arranged in the same manner but surrounded 

 by perfectly light-tight wooden cases were used. The Spongillae 

 generally kept alive for 1 — 1'j., months, in the beginning they 

 often grew strongly ; the Ephydatiae, however, sometimes lived 

 even for 5 months, but they did not grow so quickly as Spon- 

 gillae. Sometimes sponges were cultivated separately in glass 

 vessels (capacity 3 or 5 litres), also containing conduit-water, 

 though not streaming; tliis water was renewed once a day. 



The culture of the isolated cMorophytl corjMsdes. The cultures 

 were obtained in the followi^g way : A green sponge was rubbed 

 and pressed, the parts of the skeleton removed, and the remaining 

 dark green liquid mixed with some water. Then this liquid was 

 kept quiet for about an hour, during wliich time a thick green 

 mass settled at the bottom — formed, as appeared, by amoebocytes 

 and other sponge-cells and by detritus — while a still green 

 liquid remained. The latter almost exclusively contained the 

 isolated green chlorophyll corpuscles. Next this liquid was divided 

 into equal quantities over many little glass vessels; these vessels 

 were filled with the culture-media wanted to the same volume 

 (50 cM'), covered with glass plates, and placed either in (tem- 

 pered) daylight, or in complete darkness in the same room as 

 the aquaria. In the beginning the culture media were renewed 

 every 2 or 3 days (as long as there were processes of rotting 

 of sponge-rests), afterwards once in 1 or 2 months ; to which it 

 was of nuich use, that the chlorophyll corpuscles, once having 



