WATER 



In general, while it has been postulated that the differ- 

 ences in permeability noted both in a specific egg during 

 different stages of its development, as before and after 

 fertilization, and in cells of the same type, e.g., red blood 

 cells, but from different animals, are due to the membrane, 

 and that the cytoplasms are the same, the actual and visible 

 changes in the surface-layer of cells have been ignored. 

 Despite the excellent observations made by Mrs. Andrews^ 

 on the spinning activity of the ectoplasmic surface, which 

 others have abundantly confirmed, this type of rhythmical 

 surface-activity no one has sought to correlate with the 

 postulated rhythmical changes in permeability. Though 

 the measurable ectoplasmic layer of cells differs in width, 

 the size of the layer has not entered into the calcula- 

 tions made on the entrance of water. The cell is a 

 bag of watery solution; and being capable of deformation 

 with return to its normal contour and size, this property 

 of elasticity is resident in the surface-cytoplasm. But the 

 elastic property of the cell-surface has been deliberately 

 ruled out in the mathematical calculations on the entrance 

 of water into cells. On the theory that the difference in 

 rate at which water enters a specific cell in different stages 

 depends upon the permeability of the cell-surface, i.e., the 

 plasma-membrane, we should expect a most exhaustive 

 analysis of the structure and structural changes of that 

 surface — certainly we should scarcely expect that in addi- 

 tion to ignoring these the theory would actually discount 

 the elasticity of the cell-surface. 



Vitelline membranes are often chitin or chitin-like sub- 

 stance; it may be that generally they are protein; the 

 plasma-membrane also may be protein, lipin or what else. 

 These considerations lose in interest in view of the fact that 



1 Mrs. Andrews^ 1S96. 



141 



