MARINE BIOLOGICAL STATION AT PORT ERIN. 



39 



mackerel, which may feed upon young herring, and these 

 upon Copepoda, and the Copepoda again upon Diatoms. All 

 such chains of food matters from the sea seem to bring one 

 through the Copepoda to the Diatoms, which may be 

 regarded as the ultimate " producers " of food in the ocean. 

 Thus the living food of man from the waters of the globe 

 may be said to be the Diatoms and other microscopic 

 organisms quite as much as the fishes. 



Fig. 14. — Four samples of plankton taken with the same net, in the 



same locality, between April 5th and 15th, 1907, 



and ranging from 13 c.c. to 100 c.c. 



Two years ago, at the Leicester meeting of the British 

 Association, I showed that if an intensive study of a small 

 area be made, hauls being taken not once a quarter or 

 once a month, but at the rate of ten or twelve a day, 

 abundant evidence will be obtained as to : (1) variations in 

 the distribution of the organisms, and (2) irregularities in 

 the action of the nets. Great care is necessary in order to 



