The Relations between Marine Animai and Vegetable Life. 3G9 



a badly ligbted room. Here the temperature remained fairly Constant 

 at about 15° C. Nevertheless, after keeping- the water two days, the 

 niimber of germs was found to have increased enonnously in both 

 specimens of water, but especially in that kept in the jar. After a 

 fnrther two days, the nnmbers had diniinished again, though not to 

 so great an extent as they had previously increased. It would seem 

 therefore that immediately the direct rays of the snn are removed 

 from the water, the germs stili unharmed begin to multiply with 

 extreme rapidity, so that the water soon becoraes bacterially 

 much more impure than before. These rapidly multiplying germs 

 then rapidly die off, so it is possible that the ultimate bacterial 

 quality of the water may be somewhat better than originally; but 

 even this is doubtful. As the number of germs begins to increase 

 so rapidly after the germicidal sunlight is shut off from the water, 

 the cultures were generally made late in the afternoons, after the 

 water had been exposed the whole day to the sun. A determination 

 of the baeterìa present after VI2 or 51/2 days' exposure would thus 

 give very much smaller numbers of germs than if it had been made 

 after 4 or 6 days, for then the water would be examined after it 

 had been exposed for only an hour or so to the earl}^ morning sun. 



As to the primary object with which these observations were 

 made, no information is afforded. Thus on comparing the various 

 numbers obtained for water exposed in a jar to the air, with those 

 for water exposed in a flask, no Constant or appreciable ditference 

 in either direction is found. These countings of course show nothing 

 as to the quality of the bacteria in either case, hence one may be 

 allowed to explain the great differences eflfected on larvai growth 

 by the water treated in these two ways as due to the dififerent 

 degrees of oxygen tension in the water. Thus these may have caused 

 an increase or decrease in the number of certain germs with which 

 the vital processes of the larvte are closely bound up. 



ta. The Eflfeet of Keeping the Water in Darkness. 



Inasmuch as by far the larger portion of the ocean water is 

 found at depths whence no trace of light can penetrate, it was thought 

 to be of interest to determine what changes, if any, would take place 

 in sea-water kept in darkness. Accordingly, a large covered jar of 

 Aquarium tank water was placed in a cupboard, and chemical 

 analyses of it made from time to time. It should be stated that this 



