SECTIONAL TRANSACTIONS.—D. 319 
and mode of life. Specialised characters. Primitive characters. Geo- 
graphical and geological factors. Inferences. Own views on the classifica- 
tion of the Primates arising from above study. i 
Mr. D. R. R. Burt.—The correlation between climatic factors and the 
distribution of the geographical races of some Ceylon mammals (2.45). 
The different factors, temperature, relative humidity, light, altitude, 
etc., which constitute the climate in different regions of Ceylon are discussed. 
On the basis of these factors the Island is divided into three distinct zones : 
low-country dry zone, low-country wet zone, and the central hill zone 
which is also wet. ‘The geographical races of different mammalian species 
are considered and their morphological differences are correlated to the 
different climatic factors. 
There is a relation between external temperature and the internal tem- 
perature of an animal, its metabolic rate, its body size, and the ratio of the 
length of its appendages to the length of its body. The differences in the 
morphological characters of different geographical races are attributed to 
the efficiency of the temperature-regulating mechanism of the organism 
under different climatic conditions. Humidity, light and altitude modify 
the effect of external temperature on the body, the greatest effect being that 
of humidity, which accentuates the effect of temperature, preventing heat- 
loss when the external temperature is high and the main process of the heat- 
regulating system is heat-loss, and increasing heat-loss when the external 
temperature is low. 
Prof. G. D. Hate CarpPENTER.—Protective colouration in insects with 
special reference to mimicry (3.15). 
Saturday, September 8. 
Excursion to Upper Donside. 
Sunday, September 9. 
Visit to the Fishery Board for Scotland’s Research 5.8. Explorer. 
Monday, September 10. 
Joint Symposium with Section K (Botany) on Biological problems of 
fresh water (10.0) :— 
Prof. F. E. Fritscu, F.R.S.—The origins of plankton. 
Dr. W. H. PearsaLt.—The causes of algal abundance. 
Algal abundance under natural conditions appears to be primarily related 
to the oxidation of organic matter in the water, and, indirectly, to floods 
which may increase the supply of products of oxidation. Examples from 
streams, lakes and laboratory cultures suggest, however, that algal abundance 
does not only depend on the presence of an adequate supply of certain 
dissolved salts. It appears also to depend upon the balance between 
certain nutritive materials such as, for example, the ratio between the 
concentrations of nitrates and phosphates or between the nitrogen supply 
