In a recent review of the transport of salts and water across multicellular secretory tissues in animals (Keynes, 1969), a summary was given of the various types of active transport of ions necessary to explain the experimental observations in a very wide range of tissues, and five basic types of ion pump were discussed. The question of whether plants and animals have any common mechanisms for the transport of salts and water was specifically excluded. The original aim of the present review was to survey the types of ion pump found in plant cells and tissues, and to compare these with those found in animals. Its aims narrowed very considerably in writing. It now reviews ion transport processes in giant algal cells, and tries to assess progress towards understanding the mechanisms involved. It indicates the existence of similar ion transports in higher plant cells, but it does not present a complete review of the experimental work on higher plants.

The code of inheritable information which directs the synthesis of protein molecules is now known. This information is contained in the replicative molecules deoxyribonucleic or ribonucleic acid (Avery, Macleod & McCarty, 1944; Loeb & Zinder, 1961). Translation of the nucleic acid ‘information’ into protein molecules involves the initial transcription of the nucleic acid molecules into transient messenger ribonucleic molecules which are single stranded base paired complements of the more stable ‘information’ nucleic acid molecules. The events leading to the translation of the linear order of nucleic acid information in mRNA to a corresponding linear sequence of amino acids in a protein are largely elucidated at this time and will be the subject of this discussion. Since the knowledge of the genetic code is a result of data obtained from in vitro translational studies which employ the equivalent of mRNA, the genetic code is described as the RNA code rather than its DNA complement. Elucidation of the RNA code has been the focus of research activity for a large number of research laboratories over the past 10–15 years. As a result of these investigations we have a detailed description of the genetic code for life on this planet. This code appears universal in its organization and translational mechanism. Since the interactions of macromolecules necessary for genetic translation are understood with greater precision than the factors responsible for the origin of the Genetic Code, this discussion will deal in more detail with the events in the translation of genetic information.

A great deal of information about evolutionary events and processes has been inferred from careful studies of fossil records. Other forms of evidence have also contributed greatly to the understanding of evolution. Comparative biochemistry (Florkin, 1949), immunology (Boyden, 1942), protein sequencing (Dayoff, 1969; Anfinsen, 1959), and early DNA studies (McCarthy & Bolton, 1963; Schildkraut, Marmur & Doty, 1961) have for the most part corroborated earlier evolutionary findings, and at the same time provided new understanding of molecular processes in evolution. Of these approaches the comparison of DNA seems most promising since a relatively precise quantitative comparison can be made of all of the genetic material of different species.