The. Philippine Jouknal of Science, 



D. General Biology, Ethnology and Anthropologj-. 



Vol.' VI, No. 4, August, 1911. 



CONCERNING THE DEVELOPMENT OF FROG TADPOLES 

 IN SEA WATER. 



By A. S. Peabse." 

 {From the Zoological Laboratory, University of the Philippines. 



It has long been believed that amphibians are unable to withstand 

 salty water. Gadow ^ says : 



Common salt is poison to the Amphibia ; even a solution of 1 per cent prevents 

 the development of their larvae. Consequently seas, salt lakes, and plains 

 encrusted with saline deposits act as most efficient boundaries to normal 

 "spreading." 



Some observations at Manila during the summer of 1911, which 

 show that certain frogs live and breed along the swampy edges of 

 estuaries where the water is almost as saline as that of the ocean itself, 

 are of interest in this connection. 



During the month of May, the writer had occasion to spend .many 

 quiet hours along the edge of an estero ^ not far from its . opening into 

 Manila Bay. He was struck by the fact that, frogs were often seen to 

 hop about on the flats at low tide and to dodge into the crab * holes 

 filled with salty water. Pour of .. these frogs captured on July 13 were 

 all referable to the genus Rana and, though they . apparently belonged 

 to a single species, it could not be determined with the literature at 

 hand. They were all small, measuring respectively 35, 34, 32, and 18 

 millimeters in length. 



On June 17, at 8.20 in the morning the writer observed that two 

 crab holes at the edge of the estetv were filled with a wriggling mass of 

 newly hatched frog tadpoles. These holes had been seen to be left 

 above low-tide mark with water standing in them and to be covered by 

 water at high tide on each of the three days previous. On the date 

 mentioned, they were submerged by the advancing tide at 8.30 in the 



' Assistant Professor of Zoology, University of the Philippines. 

 = Gadow, H. Cambr. Nat. Hist., London (1901) 8, 72. 

 ' An estero is a small creek into which the tide flows. 

 * Sesarma Hdens { de Haaii ) . 



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