46 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



supply of nitrogen food and so limit the production of 

 Plankton. Loeb,* on the other hand, has recently revived 

 the view of Murray, that the low temperature in Arctic 

 waters so reduces the rate of all metabolic processes, and 

 increases the length of life, that we have in the more 

 abundant Plankton of the colder waters several genera- 

 tions living on side by side, whereas in the tropics with 

 more rapid metabolism they would have died and 

 disappeared. The temperature of the sea-water, however, 

 appears to have little or no effect in determining the great 

 vernal maximum of Phyto-Plankton. 



Considering the facts of photosynthesis, there is much 

 to be said in favour of the view that the development, and 

 possibly also the larger movements, of the Plankton are 

 influenced by the amount of sunlight, quite apart from any 

 temperature effect. 



Bullent showed the correlation in 1903-07 between the 

 mackerel catches in May and the amount of Copepod 

 Plankton in the same sea. The food of these Copepoda has 

 been shown by Dakin to be largely Phyto-Plankton ; and 

 Allen has lately* correlated the average mackerel catch 

 per boat in May with the hours of sunshine in the previous 

 quarter of the year, thus establishing the following con- 

 nection between the food of man and the weather : — 

 Mackerel — Copepoda — Diatoms — Sunshine. One more 

 example of the influence of light may be given. Kofoid 

 has shown that the Plankton of the Illinois River has 

 certain twenty-nine-day pulses, which are apparently 

 related to the lunar phases, the Plankton maxima lagging 

 about six days behind the times of full moon. The light 

 from the sun is said to be 618,000 times as bright as that 



* Darwin and Modern Science (Cambridge, 1909), p. 247. 

 t M.B.A. Joum., viii. 2G9. J M.B.A. Journ., vii. 394. 



