26 ANNALS NEW YORK ACADEMY OF SCIENCES 



The following views have been maintained with regard to this : Bert; 

 ('71 ) gave a minute description of the death of a fresh water fish in salt 

 water. He described the gills as changing from bright red to dark red in 

 color, and said that the congested condition of these membranes per- 

 mitted the blood to transude through them. He found the corpuscles to 

 be crenated, shriveled and piled up in masses in the capillaries. A tench 

 suspended in a vessel of sea-water lived a long time if the head was kept 

 out of the sea-water and the gills were bathed with fresh water. Fred- 

 ericq (^04) stated, '^'I can in a short time change the proportion of salts 

 in the blood of Carcinas moenas, even to doubling the quantity, if I bring 

 the animal into water more salty than sea-water. This is due to a pe- 

 culiarly modified epithelium of the gill membranes by which substances 

 dissolved in the water can go through the gills easily." With regard to 

 the fishes Fredericq said, "Les vertebres aquatiques des poissons se com- 

 portent tout differement. Chez eux, la branchie, si permeable aux 

 echanges gazeux de la respiration, semple au contraire constituer une 

 barrier presque infranchissable aux sels dissous dans I'eau de mer. La 

 sang des poissons de mer n'est guere plus sale, au gout, que le sang des 

 poissons d'eau douce." Quinton ('00), however, held the view that salts 

 as well as water can pass through the external surface membranes of ma- 

 rine animals. In a later investigation by Bottazzi and Enrique ('01), it 

 was shown that the stomach wall of the mollusk, Aplijsia, is normally 

 impermeable to salts. They concluded that the stomach wall is a semi- 

 permeable membrane, allowing the water to pass through but excluding 

 the salts, and proposed the hypothesis that osmotic equilibrium is main- 

 tained by the liver, functioning as an organ of resorption. Siedlechi 

 ('03) found that the stickleback, Gasterosteus, resisted the effects of sud- 

 den transitions from salt to fresh water and vice versa. This author held 

 that the structure of the skin amply protects the organism from the effects 

 of changes in the external medium. Schucking ('02) showed that salts 

 left the body of Aplysia, though the mouth and anus were ligated. This 

 result, together with those obtained by Quinton and Bottazzi, shows that 

 the surface membranes of Aplysia are permeable. Overton ('04) con- 

 cluded that the skin of amphibians is permeable to water and but slightly 

 permeable to salts. Greene ('05) from his studies of the Chinook salmon 

 inferred that in that species all three structures are impermeable. He 

 accounted for the fall in the osmotic pressure of the blood at the spawn- 

 ing grounds as being due to absence of food and the poor physical condi- 

 tion of the fishes. Carrey ('05) tied off both ends of the alimentary 

 canal of Nereis and Chcetopterus and found that, if placed in fresh water, 

 the animals swelled and increased in weight, which showed the permea- 



