298 REPORTS ON THE STATE OF SCIENCE, ETC. 



Decomposition of organic matter in the mud has been studied in some 

 detail. Starting from bare sand or silt it has been shown that as the organic 

 matter increases in the mud there is an increasing loss of carbon in the form 

 of marsh gas and possibly some carbonic acid gas, whereas the nitrogen is 

 retained upon the finely divided particles of mud in the form of ammonia. 

 This process increases the fertility of the lake bottom up to about 25 per 

 cent, organic content. Should the organic matter exceed this limit de- 

 composition is retarded and subaqueous peat is formed, which may remain 

 sterile or be colonised by sedges. As these changes progress the mud loses 

 calcium available for plant growth, and iron and aluminium become the 

 replaceable ions, while sulphides also accumulate ; all these substances are 

 toxic to many of the pond weeds. An analysis of plants collected in nature 

 showed corresponding changes with regard to these elements. Many 

 species were also transplanted to glass jars containing the different types of 

 muds and sunk in the lake. The crops produced from them confirmed the 

 above conclusions. 



Further methods have been evolved, including electrical appliances to 

 measure the reducing property of muds ; it has been shown that the reducing 

 property becomes stronger with increasing organic content ; as a result, 

 when the muds are kept in contact with water, the oxygen dissolved in the 

 water is rapidly used up. This is a fact of great biological importance, for 

 it means that organisms in the muds must live under anaerobic conditions. 



CYTOLOGY AND GENETICS. 



Report of co-ordinating committee for Cytology and Genetics (Prof. Dame 

 Helen Gwynne-Vaughan, G.B.E., Chairman ; Dr. F. W. Sansome, 

 Secretary; Prof. F. T. Brooks, F.R.S., Prof. F. A. E. Crew, 

 Dr. C. D. Darlington, Prof. R. A. Fisher, F.R.S., Mr. E. B. 

 Ford, Prof. R. R. Gates, F.R.S., Dr. C. Gordon, Dr. Hammond, 

 Dr. J. S. Huxley, Dr. T. J. Jenkin, Dr. K. Mather, Dr. W. B. 

 TuRRiLL, Dr. C. H. Waddington. 



Since cytology and genetics are the concern of more than one Section of the 

 Association, the Committee was formed in 1936 to assist Organising Com- 

 mittees and Recorders in arranging joint sessions and in ensuring that 

 papers of common interest were not given at the same time in different 

 Sections. 



The Committee realise that many of the facts of cytology and genetics 

 are not readily assimilated by workers in other biological fields and that the 

 difficulty is enhanced by the development of a specialised terminology. 

 They therefore approached the Organising Committee of Sections D and K 

 with a suggestion that a morning should be devoted to a joint symposium 

 and arranged for the presentation of coherent accounts of recent work in 

 their subjects in such a way as to avoid unnecessary technicalities. The 

 Organising Committee have approved this proposal. Should it be success- 

 ful, the Committee believe that the formation of such symposia and the 

 presentation of cytological and genetical demonstrations will form an im- 

 portant part of their duties, and will be of value to the members of the 

 Association. 



A number of papers have been grouped in the above-mentioned sym- 

 posium, a second series are associated in the form of a discussion on Genetics 



