218 EWNEST WARREN. 



This table requires some comment. 



The number of generations and the number of offspring in 

 the series in which the water was continually being changed 

 are seen to be far in excess of those in the other two series. 

 Thus the condition of the water arrived at by remaining in 

 the tumblers^ was prejudicial to the growth and reproduction 

 of Daphnia. 



The fifth generation of twenty-five young was produced by 

 the '*6" series at about the same time as the fourth genera- 

 tion of 12 young by ^'A" and "a" series. 



I am unable to account with certainty for the ultimate 

 weakening of the stock in the series, which had an ample 

 supply of fresh water. It is possible that the following 

 circumstance was the cause of it. 



(/3) The Effect of Sudden Transference from one 

 kind of Water into another. 



On August 3rd all the Daphnia were carefully packed and 

 taken by train under personal supervision to Canterbury. 

 They were placed on a table by an east window facing a 

 garden. The water used for series '^6" was the town water 

 supplied by the local waterworks. 



On August 5th broods were produced amounting to twenty- 

 five young, of these ten became sickly and died Avhen a few 

 days old ; also the period (eighteen days) between the second 

 and third generations was somewhat in excess of the usual 

 fortnight. The stock, however, completely recovered and 

 became perfectly healthy. 



On bringing the animals back to London and replacing 

 them in New River water some fourteen of the young died, 

 and the stock became permanently weakened. 



In October two of the families died out altogether, and the 



' Every week or ten days the water and mud were emptied out of tlie 

 tumblers, and the glass was tliorouglily cleansed i'lom the green incrustation of 

 algse, etc., which had collected on it. lu the "A" and "a" series the same 

 water was then replaced 



