The Relations between Marine Animai and Vegetable Life. 



367 



powerful diiring- the lattei- part of the experiment, and towards the 

 end the sides of the vessels became coated with a thin layer of 

 brown a\g'M. In the next experiment the following results were 

 obtained. 



Here again the rate of growth of the bacterial colonies was 

 considerably sh)wed down by eveu three hours exposure to the sun, 

 but after 48 hours, thcy were on an average as numerous as in the 

 originai water. The countings made after 6 hours and 372 days 

 show distinct gennicidal action. Nevertheless, after 15 days exposure, 

 the number of bacteria had increased again as it did before, and 

 similarly also the sides of the vessel were coated with brown alga. 

 In both these series of experiments, the vessels of water were ex- 

 posed directly to the sun, and the water in them thereby became 

 heated up to sometinies as high as 38" C. At these temperatures 

 the rate of multiplication of the surviving bacteria would of course 

 be much greater than at normal temperatures, and hence actually 

 occurring germicidal action would be partially or entirely masked. 

 In the next two series of experiments therefore the jar and flask of 

 water were placed in a larger glass vessel, through which circulated 

 a continuous streani of fresh water. By this means the temperature 

 was generally kept at about 18° and was never noticed to be higher 

 than 21". The results were as follow: 



