192 DISCOVERY REPORTS 



water molecules. The higher this is, the greater will be the viscosity of the water, and 

 viscosity is obviously an important factor for organisms whose continued existence is 

 dependent upon their ability to maintain their level. Bayliss (1927, pp. 233 et seq.) gives 

 a succinct account of the polymeric system of water and remarks that the degree of 

 polymerization is roughly inversely proportional to the temperature, a fact which may 

 well be of immense significance in the polar waters of the southern hemisphere with its 

 low summer temperatures. 



Yet another way in which the degree of polymerization may affect the phytoplankton 

 has been suggested recently, but appears hitherto to have escaped the attentions of 

 plankton workers. The first hint was given by H. T. Barnes (1928, p. 16) when he fol- 

 lowed up the well-known exposition of the fact that water is to be regarded as a system 

 of three polymers, monohydrol (steam), dihydrol, and trihydrol (ice), with the state- 

 ment that it is highly probable that the higher polymer only is utilizable by living 

 organisms. This found its natural sequel in the work of T. Cunhffe Barnes (1932, pp. 

 136, 137) when he showed that the growth of the fresh-water green alga Spirogyra 

 markedly increased when trihydrol was the predominant polymer in the culture medium, 

 under equal conditions of light and temperature. Among other biological phenomena 

 which may be explicable in terms of this trihydrol effect he mentions "the anomalous 

 increase in the plankton following the melting of the ice", and the "unexplained rich- 

 ness of microorganisms in Arctic waters . . . ". These are rather naive statements in view 

 of the many other factors known to be involved, but the possible importance of his work 

 should not be overlooked. 



In a recent contribution to Nature,^ H. T. and T. C. Barnes state that the Spirogyra 

 filaments grown in water containing less of the active polymer trihydrol resemble 

 plasmolysis forms with the chloroplasts badly twisted, and that the reduced macro- 

 scopical appearance of the cultures, compared with those grown in water with an 

 abundant proportion of trihydrol, is due to collapse of the protoplasts. These workers 

 are now engaged upon similar experiments with Protozoa. 



More recently still H. W. Harvey'^ of Plymouth has investigated the effect of varying 

 the proportion of trihydrol on cultures of the marine diatom Nitzschia dosterium, 

 by the addition of water from newly melted ice. I am greatly indebted to him for the 

 personal communication of his preliminary results, which, though not yet complete, 

 serve to show that this factor may be extremely important in polar seas. It appeared 

 that an increased proportion of trihydrol greatly stimulated the growth of the cultures 

 during days zvith long daylight, and provided that the growth was initially strong ; but 

 that earlier in the year, with short days and slow growing cultures, no appreciable effect 

 was observed. 



From the considerations outlined above, it will be reahzed that not only the melting 

 of the ice but the temperature of the water is involved in the operation of this factor, 



1 May 7, 1932, p. 691. 



2 See Harvey, H. W., 1933. On the rate of Diatom Growth. Journ. Mar. Biol. Assoc, n.s., Xix, 

 pp. 253-75: published since the above was written. 



