84 THE STORY OF LIFE IN THE SEAS. 



different circumstances the Plankton is repre- 

 sented by only a few individuals. 



The variations of the Plankton in different 

 parts of the world have, of recent years, been 

 subjected to many searching investigations, but 

 although many important facts have been re- 

 corded, the explanation of the principal pheno- 

 mena remains a mystery. 



One of the most interesting facts, perhaps, is 

 the extraordinary local variations to be observed. 

 To give a single example as an illustration of this 

 point the case of the common white Jelly-fish 

 may be mentioned. On occasions the surface of 

 the water in our bays and estuaries contains so 

 many of these animals, that the sea appears to be 

 little more than a mass of jelly. In other seasons 

 not more than a few isolated individuals will be 

 seen all through the summer months. 



With all the resources of modern scientific 

 investigation no adequate explanation has been 

 given to account for this fact. It may be that 

 the variation is due to the prevailing winds or 

 tides, to the temperature of the water, to the 

 roughness or smoothness of the sea, to disturb- 

 ance of the ground where the eggs have settled, 

 or to some other hitherto unforeseen conditions. 

 Not only seasonal, however, but even diurnal 

 variations occur, of a most remarkable and in- 

 explicable character. 



On one occasion for example I was collecting 

 a number of Jelly-fish in Southampton Water, 

 and for nearly two hours specimens were ob- 

 tained as fast as they could be hauled into the 

 boat Suddenly a change came, and in a few 



