The Relations between Marine Animai and Vegetable Life. 



413 



On comparing- tliese figures amongst themselves, it will be seen 

 that there is a slight increase of salinity on passing from the spring 

 to the sumnier and autumn months. 



The values given in the table under the heading of temperature 

 are for the water in the large tank of the Aquarium, of which the 

 capacity is about 70 cubie metres. From these it will be seen that 

 the temperature increased steadily tili it reached a maximum at the 

 end of August. From this point it at first slowly, but then very 

 rapidly, declined again. In another paper^ I bave given the daily 

 temperatures of the Aquarium water during; the winter months, and 

 from these it appears that a minimum value of about 9° is reached 

 at the beginning of January, and is more or less maintained at that 

 point tili the end of February. 



From the chemical anal}'ses of the water, it may be seen that 

 the aramonia present is very variable in amount, Thus the free 

 ammonia varies from .185 to .350 mgm. and the organic ammonia 

 from .111 to. 182 mgm. As has already beeu showu, open sea-water 

 contains about .010 mgm. of free, and .070 mgm. of organic ammonia. 

 There appears to be little, if any, relation between the amounts of 

 free and organic ammonia present, or between these amounts and 

 the temperature, or the salinity, of the water. Thus the ammonia, 

 within wide limits, keeps about the same during the whole period 

 of the observations, and such variations as are present are probably 

 only fortuitous, depending on the volumes of fresh sea-water pumped 

 luto the Aquarium, and the amount of animai life contaiued in it. 

 Thus the Aquarium water undergoes almost as great changes of com- 

 position from day to day as it does from week to week, or month 

 to month. For instance, five analyses of water taken on consecutive 

 days from one of the underground reservoirs showed respectively 



Journ. Physiol. Cambridge Voi. 19 1895 pag. 68. 



