made in connection with the present work. Plant cells 

 have, as a rule, a cell wall that completely encloses the 

 living protoplasm. The pressure in the protoplasm can 

 therefore be considerably higher than the pressure outside 

 of the cell. Oxygen is continually being produced when the 

 plant builds up organic material by photosynthesis. The 

 excess pressure in the protoplasm will increase the satura- 

 tion level required in the cell to make it possible for a 

 nucleus to grow into a bubble. 



Both Gonyaulax polyedra and Peridinium have cell walls 

 in the shape of very elaborate testa that completely enclose 

 the living cell. Nuclei produced de novo by the photosyn- 

 thetic process will therefore not develop into bubbles under 

 normal circumstances. If the outside pressure is reduced 

 rapidly, such as occurs when the water is pumped up into 

 the cavity, it seems reasonable that bubbles may sometimes 

 develop and make the organism explode. This would explain 

 the two instances where strings of gelatinous material were 

 found floating in the surface of the cavity. Pinching a cell 

 will stretch the cell wall and thereby relieve the inside 

 pressure. Cutting the cell wall will of course have the 

 same effect. If a plant cell dies, it can act as center for 

 bubbles, and the dead cell must consequently contain nuclei. 

 The excess pressure in the cell is connected with the life 

 processes, and will presumably disappear when life ceases. 

 The cell wall will often be broken by death and expose the 

 cell content, and the effect of any nuclei in the protoplasm 

 will therefore be at a maximum. 



A recent paper 3 is concerned with the absorption of 

 ultrasonic acoustic waves in water containing algae in 

 suspension. The results given indicate that a very sub- 

 stantial volume viscosity could be attributed to the algae. 

 However, the measuring frequencies were so high (15-2 7 

 Mc/s) that no reliable deductions can be made with respect 

 to the present results. 



The data presented in this investigation indicate that 

 a relationship may exist between broken cells and the 

 attenuation measured. A very clear-cut correlation could 



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