220 EliNEST WARREN. 



ing way. From much observation in breeding Daphnia it 

 seems probable that families have periods of reproductive 

 activity independent of physical conditions, such as tempera- 

 ture and the nature of the water, and perhaps in the " h " 

 families the generations on September 23rd marked the end 

 of a reproductive cycle. This supposition, however, would 

 not explain the sudden retardation in growth, and the death 

 of some of the individuals when Canterbury water was first 

 used. 



It should be remembered that the mud and tumblers were 

 in a perfectly wholesome condition ; for after the death of 

 the families on putting in fresh Daphnia from the tank, 

 broods were produced in a normal manner. 



^. The Poisonous Nature of the Water in which 

 Daphnia had been living for a Prolonged 

 Period. 



The decadence of the " A " and " a " families was un- 

 doubtedly due to the condition of the water, for fresh 

 Daphnia became sickly in it, and produced but few young, 

 and they all died in about a month. That this result was 

 not due to the mere lack of oxygen is certain, for the con- 

 ferva and unicellular algae gave off large quantities of the 

 gas. 



At the beginning of February the water was decanted 

 from the mud and conferva and filtered. It had a faint 

 brownish tinge. 200 c.c. of this water were evaporated over 

 sulphuric acid, and the residue was dissolved in about 5 c.c. 

 of water. On filtration a fairly clear amber- coloured fluid 

 was obtained. This was tested for proteids, but none wez*e 

 found. The ammonium hydrate reaction for uric acid was 

 tried, but no indication of its presence could be observed. 



Dr. Collie very kindly tested it, and he informed me that 

 he believed it contained a minute trace of an organic base, 

 but that the quantity present was so small that it was quite 

 impossible to ascertain its nature. 



