14 LIVERPOOL BIOLOGICAL SOCIETY. 



grass-gi'een seaweed, Enteroinorpha intestinalis, and on 

 this we find enormous quantities of Copepoda belonging to 

 the genus Harpacticus. The condition of some of the pools 

 suggested to me that these animals would probably be 

 able to stand considerable variations in the salinity of 

 the water, as in wet weather they are flooded with rain 

 while in dry summers the pools become almost or com- 

 pletely dried up. 



So, taking some sample tubes of salt water with Enter o- 

 viorpha and Harpacticus fulvus from the pool, I added 

 to one a third of its volume of fresh water, and con- 

 tinued every morning to add a little fresh water, until 

 at the end of twelve days there were nineteen parts of 

 fresh water to one part of the original sea-water and the 

 fluid was no longer salt to the taste. The Enteromorpha 

 appeared healthy, and the Copepoda had increased greatly 

 in numbers and were very active. The young ones hatched 

 in the nearly fresh water were all colourless, but the 

 adults had not lost their original bright red tint. 



Al second sample tube of Harpacticus, E7itero77iorplia and 

 sea-water from the pool was emptied into a shallow glass 

 dish and allowed to evaporate slowly. The Copepoda in 

 this case did not increase in numbers, but they did not die 

 until the dish was almost dry and the salt had crystallised 

 out round the edges. After evaporation had been going on 

 for a few days, I noticed that the Copepoda had retreated 

 into the interior of the Enterouiorpha filaments, where 

 their bright red bodies were distinctly visible on the green 

 ground, and I think that under natural conditions they 

 might in this way escape death when their pool became 

 dried up, as the desiccation would not be so thorough in 

 the damp atmosphere of the sea-shore as in the warm dry 

 air of my laboratory. Mr. W. J. Halls is going to take 

 this matter up and carry out some further experiments 



