220 PEARSE. 



morning and the tadpoles streamed from them into the salty water; at 

 y o'clock a tadpole was seen swimming 6 meters from the hole where it 

 hatched. At 2 o'clock in the afternoon, after the tide had begun to ebb, 

 a sample of water was taken directly over the holes where the tadpoles 

 had been observed in the morning. This was analyzed by Mr. V. Q. 

 Gana of the Bureau of Science and found to contain 18.7 parts of 

 chlorine per 1000, the equivalent of 26.44 grams of sodium chloride per 

 liter, or a 2.64 per cent solution. These frog tadpoles, then, apparently 

 developed in crab holes that were left exposed at every low tide and 

 covered by 30 and 60 centimeters of water respectively at high tide. 



On July 6 samples of water were collected from two pools, on the 

 edge of the estero, both of which contained tadpoles. The dimensions 

 of the first pool were about 3.5 by 3 meters. This pool was connected 

 with the main estero by a narrow ditch, so that the two communicated 

 at high tide. The second pool was larger, being about 10 meters square 

 and though it was connected with the estero by a ditch, was not flooded 

 with salt water so often because it was on a higher level. The tadpoles 

 taken from the first pool were nearly ready to metamorphose into frogs 

 and had well-developed legs ; those from the second pool had been hatched 

 only two or three days. Mr. Gana's report on the amount of chlorine 

 per liter was as follows : 



Grams. 

 Sample from first pool 14.851 



Sample from second pool 7.920 



The tadpoles in the former, therefore, were living in a 3.096 per cent 

 solution of sodium chloride; those in the second pool in a 1.134 per cent 

 solution of the same salt. 



The observations described show that amphibian tadpoles developed in 

 slightly diluted sea water, containing as high as 3.096 per cent of sodium 

 chloride and make it seem probable that the same thing occurred in a 

 8.G44 per cent solution. 



