320 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



lighted side of the vessel. The water should be poured off 

 at intervals through. a fine silk sieve, which retains the 

 nauplii and is afterwards washed into formalin. Fresh 

 sea-water is added to the vessel and the process repeated 

 from time to time. After twenty-four hours practically 

 all the nauplii will have hatched. To get at the 

 approximate number of nauplii produced by a single 

 individual, take a definite number of barnacles, say ten, 

 and collect all the nauplii till hatching ceases, then dilute 

 the collection with water to a working volume and count 

 the number of larvae in several separate cubic centi- 

 metres drawn off from the well-shaken mixture with a 

 wide pipette. The average of these samples is multiplied 

 by the number of cubic centimetres representing the 

 working volume, which gives the total nauplii present. 

 The figures obtained are then divided by ten to give the 

 approximate number of nauplii produced by each 

 barnacle. This number varies with the size and age of 

 the adult. We found from experiments that the large 

 and probably full-grown adults yielded 9,000 nauplii, 

 whereas half -grown ones produced only 3,600. If we 

 take the average as 6,000, which is probably a low amount, 

 and let this represent the number of nauplii produced by 

 every barnacle along the coasts of Lancashire, Wales and 

 the Isle of Man, it is clear that the zoo-plankton in a 

 barnacle region must be subject to enormous but very 

 temporary increases in the early spring by the advent of 

 these larval forms. 



The local abundance of adults on rocky coasts, such 

 as Wales and the Isle of Man, must give rise to enormous 

 swarms which have a very great influence on the volume 

 of zoo-plankton in the neighbourhood. There can be no 

 chance of a uniform distribution taking place over such 

 an area as the Irish Sea, because, apart from the natural 



