210 SCIENCE PROGRESS 



that such will be discovered. It will at once be obvious that 

 the different behaviour of these organisms with regard to 

 temperature explains why it is that inorganic nitrogenous 

 substances are more abundant in the warmer than in the colder 

 seas. At the temperature which obtains in the former they are 

 able to carry on their work of breaking down nitrates and 

 nitrites, while in the cold waters of the arctic seas, where the 

 temperature may be for many months in the year little, if any, 

 above that of freezing-point of fresh water, the activity of the 

 denitrifying bacteria is inhibited or arrested, with the result that 

 the compounds of nitrogen are allowed to accumulate. In the 

 temperate seas intermediate conditions are encountered. 



So the antithesis between the sea and the land with respect 

 to the distribution of life according to temperature is most 

 probably to be explained. Those organisms which exhibit a 

 plant-like mode of nutrition are more abundant in the colder 

 or temperate seas, because they there have a greater amount 

 of foodstuffs at their disposal ; and with the abundance of the 

 diatoms, and the organisms with a similar mode of feeding, 

 stands the abundance of the animals which feed directly, or 

 indirectly, on these lower forms of life. There must always 

 be an exact relationship between the producers and the con- 

 sumers, the latter varying in abundance with the abundance 

 of the former. The scarcity of the ultimate foodstuffs in the 

 warmer seas is due to the greater degree of denitrification that 

 goes on there. We cannot suppose that this same amount of 

 denitrification takes place on the land, and so life in the 

 tropical countries is more abundant than in the cold ones, 

 the more favourable physical conditions of the former being 

 allowed to influence the production unchecked by other inimical 

 factors. 



