1. Haldane, J. S., The Sciences and Philosophy (Hodder and Stoughton, London, 1929).
2. Bertalanffy, L. von, Theoretische Biologie (Gebröder Borntraeger, Berlin, 1932).
3. Russell, E. S., The Directiveness of Organic Activities (Cambridge Univ. Press, 1946).
4. Spinoza, B. de, Ethices, pars. III. Prop. VII, 102 (1677). (cf. Arber, A., Biol. Rev., 16, 81 (1941)); also ref. 3, 191.
5. Oparin, A. I., Life, its Nature, Origin and Development (Oliver and Boyd, Edinburgh and London, 1961).