400 



H. M. Vernon 



Here we see that with .0394 gm. of ammoniuni chloride per litre, 

 or one part in 25,400, only 28^ of the fertilised ova reaehed the 

 eight days' larvai stage, and vvere then diminished 19.0^0 in size! 

 With larger quantities of the salt, not only were no larvae obtained, 

 but a considerable proportion of the ova failed even to reach the 

 blastula stage. Finally the addition of one part in 1270 of the salt 

 caused the fertilised ova to rapidly disintegrate. 



This exceediügly iojurious action of ammonium salts is rendered 

 more striking wheu compared v^^ith that of nitrites and nitrates, bodies 

 v^hich, as is well known, are very frequently the producta of bacterial 

 oxidatiou of ammonia, both in the soll, and in water. In the accom- 

 panying table the effects produced by the introduction of small 

 quantities of potassium nitrite and nitrate into the water are given. 



These results are somewhat variable, but they may be taken to 

 show to show that when less than about .3 gram of potassium nitrite 

 or 1 gram of potassium nitrate per litre are added to the water, the 

 eflfect produced on the larvai growth may be nothing at all, or 

 slightly positive. Thus the percentages of ova reaching full larvai 

 development seem to favour the existence of a definite positive action, 

 they being respectively 89.5 and 96.5^ when the quantities of nitrite 



