﻿200 BLIND VERTEBRATES AND THEIR EYES. 



Observations between August 22 and 25 showed slightly higher temperature for 

 open caves, thus: in June, 1905, the temperature at Banos was 75.8°, at Ashton, 

 75.6°, and on August 25, 1904, it was 77° at Banos and the same at Ashton. In 

 the "M" Cave, a closed one, the temperature was the same, 75° Fahrenheit. 



The blind fishes are adjusted to withstand slight fluctuations in temperature. 

 Some were kept in aquaria and the water became distinctly chilled over night and 

 warmed during the day. While they lived for several days in these aquaria, they 

 were always sluggish or numb in the morning. A more distinct reaction of the 

 same sort was noticed in the only fish I succeeded in bringing home alive. It could 

 scarcely move after an early September night in Indiana. A still greater reaction 

 was noticed in several I succeeded in bringing alive to Louis\alle and which suc- 

 cumbed to the frosty weather on the way from the depot to the hotel. 



TRANSPARENCY OF WATER. 



In all caves in which collections were made the water is clear as crystal. It 

 will easily rank with the water of Lake Tahoe and of the limestone springs of Florida, 

 as among the most transparent natural water in the world. Fishes can readily 

 be seen at depths of 15 and 20 feet or more, with the aid of a bicycle acetylene lamp. 

 The water at the Vento Spring is of the same nature, but I was informed that it 

 becomes slightly roiled after heavy rains. 



CHEMICAL COMPOSITION OF WATER. 



The water is everywhere highly charged with salts of lime and magnesium 

 In all cases where the surface of the water is not disturbed by breezes, a crust of 

 these salts forms like a thin ice over the surface of the water. When one disturbs 

 the water, the crust breaks up into small fragments which fall through the water 

 like snow through the air. Occasionally a larger flake, a foot square, may fall to 

 the bottom ; sooner or later they are dissolved again. With falling of the level 

 of the water some of the crust is left on shore and gives an index of the amount 

 of rise and fall in the water during a year. 



FLUCTUATION IN AMOUNT OF WATER. 



The ordinary fluctuation in the amount of water in the caves is very small — ■ 

 about one foot during a year — judging by the flakes of lime left on the banks. 

 I have mentioned elsewhere that, after long-continued rains, water flooded the 

 entire region about Modesta, the cave was full to the top, and the water stood 

 several feet over the ground. All of this retreated in a few days. Such fluctua- 

 tions are very rare. 



SIZE OF ENVIRONMENT. 



Concerning the size of the environment little can be said. The pools accessible 

 are easily measured, none of them exceeding a few square meters in surface, 

 but the size of the underground connections is naturally unknown. The rapid 

 disappearance of the water after heavy rains indicates extensive underground 

 channels. 



