A Brief History of a Marine Tank. 263 



filled with sea-water. I put in about half-a-dozen tufts of 

 Ulva and Enteromorpha, and after four days had elapsed I 

 stocked it with animal life as follows : — Six Actinia mesem- 

 bryanthemum, two Sag artiaviduata (anguicoma), four Sag artia 

 bellis, four Bunodes gemmacea, two Sagartia dianthus, one fine 

 block of Gorynactis viridis, and twelve periwinkles. I left all 

 alone for a week, and at the end of that period most of the 

 zoophytes had shrunk up, refusing any longer to display their 

 gorgeous rays of flowery tentacles, and a black spot in one 

 corner told of a death that had occurred. I soon found that 

 the defunct party was a periwinkle, and he was removed. 

 Three or four days afterwards a slimy appearance and a slight 

 cloud indicated another death, and this time it was one of the 

 Bunodes gemmacea. The next day I lost a mesembry- 

 anthem.um. 



When the last corpse was removed, a cloud rose from the 

 spot where it had lain — the thermometer in the room being 

 then at 83°, and the water was in a bad state. I was 

 compelled, therefore, to remove the animals to a shallow 

 pan, and leave them uncovered for a time, while I filtered 

 enough water through charcoal to enable me to cover them 

 with a thin film. The remainder of the water was exposed in 

 a vessel to the sunshine for three days, and the empty tank 

 was well cleansed and dried, and the shells exposed to sun- 

 shine to effect a perfect purification. While in the shallow pan 

 I lost .my block of Gorynactis — every one perished. The tank 

 was refitted, but the water was by no means so bright as when 

 it was dipped from the salt sea. I made good what had been 

 lost by evaporation by adding fresh water till the specific 

 gravity bulb showed an inclination to sink. The same day a 

 fine dianthus floated about instead of adhering; all the rest 

 adhered well, and there was a fine display of tentacles, as is 

 commonly the case after the animals have been disturbed. I 

 removed the dianthus, and gave him a vessel to himself; but 

 he never took hold, and died without a murmur. In the course 

 of the summer I lost two more periwinkles : but though they 

 lay some time decomposing before I knew it, I did not disturb 

 the water, being content to remove them quietly, and leave the 

 water and its inmates to fight it out. 



From the time of first fitting the tank to last Midsummer- 

 day was a period of three years. On that day, considering the 

 experiment satisfactory and sufficiently lengthened out, I dis- 

 tributed the little collection. At the time of distribution the 

 stock consisted of five A. mesembryanthemum, two S. viduata,. 

 one S. dianthus, four S. bellis, four B. gemmacea, and eight 

 periwinkles. The state of the tank was also very different 

 to what it was for some months after the first furnishings 



