1902-3.] Sawdust and Fish Life. 441 



the purpose of getting information on this point two series of experi- 

 ments were carried on, one with cedar sawdust and one with white pine. 



Extracts from Cedar (Ontario). 



On the second of June 400 grams of cedar sawdust were placed in 

 a cheese-cloth bag and sunk to the bottom of a small glass aquarium 

 (12 in. X 8 in. x 6 in.) containing 7,000 c.c. of tap water. Next day- 

 there had formed at the bottom, to a depth of two inches, a dark yellow- 

 ish brown solution. The uppermost four inches were tinged a light 

 yellow by diffusion, but there was a perfectly distinct surface of a greyish 

 colour separating the upper from the underlying dark water. These 

 characters became still more marked during the week, at the end of 

 •which time 1,400 c.c. of the lower liquid were siphoned off into a shallow 

 circular dish and a perch weighing seventy grams immersed in the solu- 

 tion. In thirteen minutes it was lying on its back moribund, but revived 

 when returned to fresh water. The control animal was kept twenty-four 

 hours in 1,400 c.c. tap water in a similar vessel and then returned to the 

 aquarium. 



A perch weighing twenty-five grams was placed in 400 c.c. of this 

 extract and air bubbled rapidly through it all the time. In twenty- 

 eight minutes it was dead. The control animal in tap water under 

 similar conditions was alive at the end of seventy hours. 



Three Daphnice in this extract died within two hours. 



Fresh water Hydra died almost instantly in it. Paramoecia were 

 unaffected by either cedar or pine extracts. These scavengers were often 

 observed apparently feeding upon the dead bodies of Hydra that had 

 died in the poisonous extracts. 



On the 13th, all the water was poured off and fresh water added. 

 On the 14th, a perch weighing seventy grams was placed in 1,400 c.c. 

 of the solution formed during the preceding twenty-four hours. It was 

 moribund in six minutes. With air bubbling rapidly through some more 

 of this solution, another perch placed in it was moribund in seven 

 minutes. 



Pond silk appeared to be unaffected by an immersion of four days 

 in this water. 



June 15th. A perch moribund in fourteen minutes in a third solu- 

 tion — all the water being poured off and fresh added. 



