134 Papers from the Marine Biological Laboratory at Tortugas. 



same type of salt solution for comparative results. As stated above, Mg- 

 free sea-water of 0.6 m. concentration was employed. 



The magnitude of the difiference between pure NaCl and a balanced 

 medium is brought out in table i. 



Table i. 



PART I. THE PERMEABILITY OF MARINE TISSUES. 



PENETRATION RATE AND DEGREE OF DISSOCIATION. 



Just as in the case of fresh -water organisms (Paramcecium, Spirogyra, 

 Elodea), the weakly-dissociated alkalies (group i) penetrate marine tissues 

 almost instantly, the strongly dissociated only after an interval of 30 to 60 

 minutes. This statement applies to all the cells or tissues of salt-water 

 organisms investigated, including the following: 



Holothuria floridana, immature eggs. 

 Holothuria floridana, respiratory tree. 

 Hipponoe esculenta, mature eggs. 

 Toxopneustes variegatus, mature eggs. 

 Toxopneustes variegatus, plutei. 

 Sabella sp., tentacles. 



Eunice fucata (palolo-worm), segmenting eggs. 

 Eunice fucata (palolo-worm), trochophores. 

 Pomatostegus stellatus, mature eggs. 

 Cassiopea xamachana, gonads. 

 Cassiopea xamachana, subumbrella epithelium. 

 Two unidentified species of marine algae. 



Thus, the anomalous result again appears that it is the least dissoci- 

 ated, the weakest group of alkalies, which penetrate living cells most 

 rapidly. Two of the members of this group are considerably less dissoci- 

 ated than the rest ammonia and trimethylamine. We might expect them 

 to penetrate most rapidly of all if rate of penetration bears an inverse relation 

 to degree of dissociation. There is, however, no marked difference in pene- 

 tration rate between ammonia or trimethylamine and the other amines,^ 

 but a well-defined difference in toxicity. 



TOXICITY AND DEGREE OF DISSOCIATION. 



The lower toxicity of ammonia and trimethylamine is indicated in 

 table 2. Efficiency in preventing development of the sea-urchin's egg and 

 cytolytic action were taken as criteria of toxicity. In addition to ammonia 

 and the amines, tetraethylammonium hydroxide was also studied. Al- 

 though a substituted ammonia, it is strongly dissociated, ranking with 

 the inorganic alkalies, and in table 2 it may thus serve as a representative 

 of the inorganic alkalies. The unfertilized eggs were placed in the solution, 

 and a certain number removed to sea-water after intervals of 2 and 5 minutes 

 and fertilized. 



6 Ammonia and the amines enter cells so rapidly that it is impossible to detect constant differences in pene- 

 tration rate. 



