146 Papers from the Marine Biological Laboratory at Tortugas. 



mentally changing the normal nature of the cell-surface. The manner 

 in which cytolysis is connected with such a change in the cell-surface may be 

 conceived as follows: 



The NaOH combines with substances, probably with proteins at the 

 surface of the egg, forming a compound through which it may pass; i. e., 

 the surface is made permeable to NaOH. This compound must also allow 

 the salts of sea-water to pass readily ; the egg is likewise made permeable to 

 the salts of sea-water.^^ Osmotic equilibrium is upset and the egg absorbs 

 water and salts. Breaking up of the granules is due largely to the increase 

 of water in the egg. All marine eggs swell when placed in fresh water and 

 when the increase in volume reaches a certain value the contained granules 

 break down; true cytolysis results. The breaking-up of the granules by 

 distilled water is obviously not due to any chemical substance, such as 

 alkali, entering the egg. An increase in permeability might result in swelling 

 without the entrance of the cytolytic substance. Such is the case when 

 Cumingia eggs are placed in NaOH. 



However, I am inclined to think that the presence of a sufficient number 

 of OH ions within the egg may aid in the breaking down of the granules 

 and that this breaking down increases also the degree of swelling of the egg. 

 Cytolysis in Holothuria appears to be largely of this type, since here NaOH 

 enters before the increase in volume begins. 



From this point of view both theories of cytolysis contain an element 

 of truth. Swelling of marine eggs is due both to an increase in permeability 

 of the surface and also to the breakdown of lipoid or protein granules 

 within. The latter tends to increase the swelling pressure or the osmotic 

 pressure of the egg, but is secondary to the increase in permeability of the 

 surface. 



^ McClendon (Am. Jour. Physiol., vol. 27, p. 240, 1910) finds the electrical conductivity in sea-urchin's 

 eggs to be greatly increased after cytolysis, a result indicating ready passage of the salts of sea-water. 



