ZOOLOOICAL AND BOTANICAL ASSOCIATION. 7 



22nd (evening). All are dead, without exception, in both jars. 



Second Experiment. — A glass jar, one foot high, and filled with fresh 

 water, had a diaphragm of net extended across the middle of it, and was 

 so arranged that twenty tadpoles were confined in a compartment below 

 the diaphragm, and were consequently unable to reach the surface, 

 while twenty more, placed above it, had free access to the air. After 

 the lapse of twenty-four hours, all those below the diaphragm were dead; 

 none of those above it ; these latter lived for many weeks, but none of 

 them developed into frogs. This jar stood in the window ; these tad- 

 poles were not specially fed. 



Third Experiment. — Six tadpoles, very young, and all having the 

 external branchiae still in existence, were placed under a small bell-glass 

 completely filled with water, and standing in a saucer, so that not a single 

 bubble of air was within the bell of the glass ; all were dead in twenty- 

 four hours. 



Fourth Experiment. — One dozen of well-grown healthy tadpoles 

 were put into an earthen vessel (a marmalade pot) 4 inches deep, and 

 4 inches wide at the mouth. Over the mouth of the vessel was tied a 

 piece of net to prevent the tadpoles from getting out, and by the aid of 

 a string it was let down to the bottom of a large crock containing six 

 gallons of fresh water. Every day the water in the large crock was 

 stirred violently, so as, in some degree, to aerate the water, and the tad- 

 poles were examined daily. 



On the ninth day from the commencement mortality began; on the 

 fifteenth day every one of the dozen were dead. 



18th. — Fifth Experiment. — Five dozen and four tadpoles, most of 

 which had just lost the external branchiae, were put into a tin canister, 

 the mouth of which was tied over with a net to prevent their escape ; the 

 canister was let down five to six feet into a river, in which there was 

 not a very rapid stream. Ten dozen similarly circumstanced were 

 lowered into a large tank of stagnant water, — this experiment being set 

 on foot in the country, some distance from Dublin, I was not able to 

 watch the progress of it daily. I can, therefore, only state that — 



25th. The tadpoles which were this day week put into the river and 

 tank at Kihharvan were taken up, found lively, tied up again, and re- 

 turned. 



May 23rd. Four weeks later all were dead in both river and tank.^ 



These experiments show that an abundant supply of oxygen is one 



