The Kelations between Marine Animai and Vegetable Life. 375 



The values given for the ammonia in the normal Aquarium 

 water are for the specimens of water in whìch were grown the larvse 

 taken as ,normal', and against which the larvìe grown in the waters 

 exposed to darkness were compared. They do not represent the 

 composition of the water before purification by keepiug in darkness. 



From the values given in the last column of this table, one may 

 see that in almost ali cases the larvse were eonsiderably increased 

 in size, in two instances by more than \1 %^ but as a rule by about 

 5^. The great increase in size in the first two experiments given 

 in the table was probably in part due to the dwarfing of the , normal 

 larvae, by the very impure water in which they were grown. Thus 

 in Exp. 82, in which the water had been purified to a much greater 

 extent, the larva? were only 4.2^ larger than the normal, but on 

 the other band the water in which the normal larvie were grown 

 was much purer than before. In Exp. 83, the water used had been 

 kept in darkness for the same lengtii of lime as that in Exp. 82, 

 but, as already mentioned, it was previously ,seeded' by the addition 

 of a small quantity of water which had itself been kept in darkness 

 for 31 days. With this water the larvse were increased by \\A%, 

 so that the seeding seems to bave induced an increased physiological 

 purification. In Exp. 86 was used the water which had, before 

 keeping in darkness, been heated to 100" C. The larva) are in this 

 instance actually diminished in size by 3.4f^, whilst in a sample of 

 the same water after 55 days darkness, and in which very much 

 more of the ammonia present had been absorbed, the larvai were 

 practically unaffected. In Expts. 116 and 119 were employed samples 

 of the same water as was used in Expts. 82 and 83, which had 

 however been kept an additional 30 days in darkness. The favourable 

 effects produced were not so great as before, the larva? being increased 

 in size by respectively 3.0^^ and 5.0^, instead of 4.2^ and \\A%. 

 This may bave been due to the water in which in the , normal' larvse 

 were grown being more favourable to larvai growth in the latter 

 instance than in the former. In any case one is justified in concluding 

 that the water had undergone little or no increase in , physiological' 

 purity durìng the extra 30 days, just as it had undergone no increase 

 of chemical purity. 



Lastly in Exp. 128 the larvse were only very sligtly affected, 

 but it should be noted that the Aquarium water was on this occasion 

 even purer, in regard to its organic ammonia, than the water kept 

 in darkness. 



25* 



