Organization and Control in Prokaryotic and Eukaryotic Cells

their metabolism. The problem of the ecological effects of these insecticides is not discussed in detail. The review by Kinsky of "Antibiotic interactions with model membranes" deals with the fascinating class of compounds that can do tricks like incarcerating potassium ions in a clathrate cage, allowing them to pass with relative ease through the normally hostile hydrophobic territory of lipid layers. Himwich and Alpers review "Psychopharmacology." In view of the amount of money spent on, and made out of, the drugs concerned, it is sad that the consensus is, ".. . in the management of anxiety, meprobamate, chlordiaze-poxide, diazepam, and oxazepam are slightly better than barbiturates and all are somewhat better than placebo." Among the other topics dealt with are cyclic AMP and drug action, the pharmacology of viruses, antifertility agents, L-asparaginase and aerospace problems. On these doubtless splendid reviews I have neither the space nor the competence to comment. Despite the enormous variation in complexity among living organisms, the cells of which they are composed represent only two general types: pro-karyotic and eukaryotic. The more complex eukaryotic cell is the unit of structure in animals, plants, and in three broad groups of protists: fungi, protozoa, and all but one group of algae. The less complex prokaryotic cell is the unit of structure in two protistal groups-the bacteria and blue-green algae. The introductory chapter of this symposium, by R. Y. Stanier, describes with great clarity the principal differences between prokaryotic and eukary-otic cells, and speculates on their possible evolutionary relationships. These relationships are difficult to imagine, since the principal organelles which characterize the eukaryotic cell are believed to have evolved from prokaryotic endosymbionts. If mitochondria and chloroplasts, for example, have evolved from endosymbionts, then what would the original host cells have been like? Stanier suggests that they may have been cells which had evolved the capacity to perform endocytosis (phagocytosis and pinocytosis); the symbiosis between such a cell and one possessing the respiratory apparatus, for example , would have had a major selective advantage. The eukaryotic cell, in addition to performing endocytosis and harboring DNA-containing organelles, differs from prokaryotic cells in a number of ways. Principal among these differences are the possession of an elaborately organized nucleus, an endoplasmic reticulum, and microtubular systems which underlie such activities as mitosis, intracellular translocations, and ciliary movement. Prokaryotic cells not only lack these features, but also possess a number of unique features not …