PHASES OF DIVIDING SEA-URCHIN EGG. 125 



undergoing a reversible increase in permeability at the time of 

 cleavage. If a rhythm of alternate increase and decrease of 

 permeability accompanies the rhythm of the mitotic process, it 

 seems logical to infer that the entrance of solutes into the cell 

 would occur most readily when there is a loss of semi-permea- 

 bility. Accompanying this change would be a decrease of the 

 electrical surface-polarization, and this in turn probably would 

 alter the metabolic processes, especially oxidations within the 

 cell. Cell metabolism then is inseparably bound up with cell- 

 permeability; and the plasma-membrane, or semi-permeable 

 surface-layer is something more than a haptogen membrane (to 

 which it has frequently been compared). In discussing this 

 subject in a later paper, Lillie 1 makes it especially clear that this 

 ''general characteristic of semi-permeability (the all-essential 

 insulating and diffusing-preventing property) is not merely the 

 result of a special chemical composition and structural density, 

 such as determine the semi-permeability of a precipitation- 

 membrane, but is inseparable from the living condition, i.e., is 

 actively maintained by a continual process of metabolism. The 

 proof of this is that death the cessation of metabolism how- 

 ever caused, is invariably followed by a loss of semi-permeability, 

 i.e., the normal state of the membrane then ceases to be main- 

 tained and the unhindered processes of diffusion lead to the 

 disintegration of the cell. Hence destruction of the surface- 

 layer by artificial means cytolytic substances, heat, extensive 

 mechanical injury is quickly fatal to all cells." 



In the experiments about to be described, I have studied the 

 behavior of fertilized Arbacia eggs when subjected for definite 

 brief lengths of time to various concentrations of some of the 

 higher alcohols anyl, hexyl, heptyl, octyl and capryl at differ- 

 ent periods of the cell-division cycle. This work was undertaken 

 at the Marine Biological Laboratory, at Woods Hole, Mass., 

 during the past summer at the suggestion of Professor Ralph 

 Lillie, to whom the writer expresses his hearty thanks for many 

 kind suggestions and directions during its prosecution. 



1 R. S. Lillie, Amer. Journ. Physiol., 1918, Vol. 45, No. 4, p. 406. 



