Dilution and Salation 41 



Virginia, Reese (1932) says: Cave crickets and certain Diptera 

 were found in practically all caves; bats in the majority of the 

 caves; fish and salamanders in a few caves. No blind fish were 

 found. Blind beetles were the only blind animals seen." In this 

 case the animals mentioned as being abundant are all recent spe- 

 cialized types. 



The soil and the caves included below it contain few animals that 

 have spread from the ocean or fresh water into them. A few such 

 subterranean animals are primitive, but the majority are apparently 

 derived from modern types which have spread from epigean 

 habitats. 



Dilution and Salation 



Of the earth's surface 73.4% is ocean and 26.6% is land. The 

 salinities of various enclosed parts of seas are somewhat different. 

 The Caribbean and Gulf of California are "normal" with salinities 

 of 35-36 and 35-35.5; the Red Sea (37-41), Persian Gulf (37-38), 

 and Mediterranean Sea (37-39) are above normal; and the Arctic 

 (20-35), Japan (30-34), China (25-35), and Baltic (3-15) Seas 

 are below normal (Jenkins, 1935) . 



Many littoral marine animals are able to live in diluted sea water 

 (Vaughan, 1919; Fredericq, 1922) . Such types as the worms of the 

 genera Nereis and Laonice and the king crab, Limulus, will live for 

 weeks in a mixture of one quarter sea water and three quarters 

 fresh water (Pearse, 1928) . Some animals (echinoderms) in which 

 the body fluids are nearly isotonic with the surrounding medium are 

 killed when obliged to live in diluted sea water, but others (certain 

 crabs and fishes) can survive gradual or even sudden changes. The 

 hagfish, a primitive cyclostome, has body fluids which are isotonic 

 with the surrounding medium. "The chloride content of the blood 

 of the hag-fish, Polistotrema stouti (Lockington) , is comparable to 

 that of the marine invertebrates, and it is probable that part of the 

 body wall of this species is freely permeable to water and salts. 



