RICHARD L. WOOD 67 



terminal bar but no farther. Thus, at least for higher forms, large 

 molecules do not penetrate between cells and the traditional inter- 

 pretation of the terminal bar as a device for sealing the intercellular 

 spaces now has some experimental substantiation. 



HESS: Some substances might even use those cross striations as 

 the steps of a ladder to climb into the hydra. 



WOOD: I've thought of these cross connections as a system of 

 baffle plates that might slow down penetration between the cells. 



