— 
RE ger 
On a gigantic colony of Thread-Bacteria from the 
West Indies. 
By 
Dr. Th. Mortensen. 
During a visit to the Danish West Indies in the winter 
1905—66 I had occasion to study the organic life in the rock 
pools, especially on the small Island Loango Cay, situated between 
St. Thomas and St. Jan. These rock pools åre more or less 
above the level of the sea. The lower ones have a constant 
renewal of the water, every wave rushing into them, while the 
upper ones have their water renewed only by higher sea, thus 
sometimes remaining for a long time without connection with the 
sea. The water in these latter accordingly must reach a very 
high temperature, directly exposed, as it is, to the burning rays 
of the sun; also the salinity must, of course, be increasing con- 
siderably through the constant evaporation of the water. Some 
very small rock pools on the neighbouring Island, Congo Cay, I 
found seven covered with a thick, clear crust, like ice — the 
erystallized salt! — Unfortunately I have no direct measurements 
of the temperature and salinity of the water of these pools. 
The organic life found in the rock pools is exceedingly inte- 
resting and most varied. Those pools, where the water is constantly 
renewed, are especially rich. Actinians, Corals, Sea-Urchins and 
different small Algæ cover the bottom and the sides, while numbers 
of Ophiurans and worms are found below the stones on the bottom. 
Also several beautifully coloured small fishes almost constantly 
occur here, In the pools higher above the sea-level life gradually 
Vidensk. Meddel. fra den naturh. Foren. 1908. 10 
