The Mechamsm of Ciliary Movement. 



129 



M/2 NaCI Ph 7 '8 No recovery. Cilia remain healthy, but cells 



absorb water rapidly. 



i Sea-water I'u 7 '8 Cilia at once become opaque. Cells rapidly 



absorb water. 



M/2 KC1 Ph 7 '8 Marked recovery of beat : recovery is temporary. 



and cells rapidly swell. 



If, whilst the period of recovery in M/2 KC1 is well marked, the gills 

 are transferred to sea-water or to any solution containing calcium, the cilia 

 instantly become opaque, and the cells swell rapidly. It is clear, therefore, 

 that although such cilia may beat rapidly in the presence of potassium 

 chloride, yet the semipermeability of the cell-wall has been entirely 

 destroyed by the previous treatment with sodium citrate. The only metal 

 capable of re-stabilising the cell-wall is magnesium. 



A further study of this problem obviously leads to a consideration of the 

 nature of the cell-membrane itself, and although our knowledge is very far 

 from complete, interesting analogies may be pointed out in the case of non- 

 living systems. One of the most characteristic features of cell-membranes 

 is their capacity for allowing weak alkalies and acids to pass into the cell 

 and yet exclude the strong alkalies and acids. These facts have, of course, 

 led to the suggestion that the cell-membrane is essentially lipoid in nature — 

 or that, at least, it contains a lipoid phase. Now Clowes (2) has shown 

 that the nature of an oil and water system depends upon the nature of the 

 ions present in the system. The truth of this statement may be very 

 simply verified as follows : — Into five test-tubes are placed 10 c.c. of olive 

 oil containing a little oleic acid, and an equal volume of test solution, 

 together with 0"5 c.c. IST/10 NaOH. The tubes are then thoroughly shaken 

 by hand, and examined after about five minutes. 



Clowes maintains that a system of water-drops in a continuous phase 

 of oil may be converted into a system of oil-drops in a watery phase by 

 means of sodium chloride. It must be pointed out, however, that grave 

 difficulties attend the suggestion that the surface of the cell possesses a 

 continuous oily phase ; nevertheless, these experiments indicate the possible 

 mode of operation of bivalent metals on the cell-surface, if the latter in 

 any way resembles an oily emulsion. 



In some ways an even closer analogy to the experiments described in 

 this paper is provided by the experiments of Schryver (10). This author 

 has shown that when a 2 per cent, sodium cholate solution is heated in the 

 presence of calcium a gel is formed. This gel is eroded by solutions of the 

 salts of monovalent cations, but is completely stable when in contact with 

 a solution of balanced monovalent and divalent cations. The erosive power 



