1902-3.] Sawdust and Fish Life. 445 



9.45 a.m. of the i8th, twenty out of one batch of thirty-three were dead ; 

 and in the other, thirteen out of seventy-three were dead. At 5.30 p.m. 

 of the same day all of the first batch of thirty-three were dead, and 

 only seven were alive in the other. 



The effect of aerating the pine water was made apparent in another 

 way. At 10.25 a.m. of the i8th, 120 eggs were placed in pine water in a 

 shallow dish so that the water was only three-eighths of an inch deep. At 

 5.20 p.m. only a few were dead ; all the rest were very quiet. At 9 a.m. 

 the next morning forty-seven were dead ; at 6 p.m. all were dead except 

 five. At 10.30 a.m. of the 20th four of these five had hatched out and were 

 quite lively. This experiment shows that the large surface exposed to the 

 air absorbs oxygen, and therefore tends to prolong the life of both larvae 

 and fry. In contrast with this it is interesting to note that the same 

 quantity of poisonous water put into a tall jar at 6 p.m. of the 19th had 

 killed every egg in a batch of nineteen by 10.30 a.m. the next morning. 

 In this case, the depth of the water and the small surface exposed to the 

 air prevented the diffusion of the oxygen downwards to the eggs, lying 

 at the bottom of the vessel. 



There can be no doubt that fish instantly perceive the poisonous 

 character of pine or cedar extracts. A minnow was placed in the 

 large marble aquarium already described, and being driven to one end 

 of the vessel, it sank through the clear water and into the yellowish 

 brown extract lying at the bottom. The moment his head touched it 

 he started towards the surface. I drove him back several times, and 

 each time he sank into the coloured water he made frantic efforts to 

 escape from it. He refused finally to be driven into it. Immersed 

 in the pine extract in a separate vessel the minnow was moribund in 

 three minutes and could not be resuscitated in fresh water. 



A perch placed in 900 c.c. of pine water, in a shallow dish, was 

 moribund in three minutes. 



Another perch in pine water with air bubbling rapidly through it 

 lived three and a half hours. 



Two limicolous worms died in thirty minutes ; tvvo rotifers lived 

 only ten minutes. 



One tadpole half an inch long lived two hours. Another tadpole 

 of the same size died in half an hour in a weak solution. A similar 

 animal in strong cedar extract lived only six minutes. 



A copepod placed in it at 11 a.m. was alive at 3.30 p.m., but died 

 during the early evening. 



