Investigations of the effects of valinomycin on mitochondria" 2 led to the discovery of antibiotic-mediated ion transport.3 Subsequent work revealed that this property is shared by valinomycin, the enniatins, the macrolide actins, and the gramicidins, including an extensive array of natural and synthetic analogues.4-6 Passive ion permeability effects have been reported obtained with these agents on other systems including erythroeytes,7 synthetic lipid vesicles,7 and artificial bimolecular lipid leaflets.8' 9 The macrolide actins can even mediate cation transport, as detected by biionic potential development across a bulk phase of CCl4.l1 All these antibiotics, which have in common low molecular weights (ca. 500-1500), a curious alternation of D and L configurations, lipid solubility, and a lack of ionizable groups, will be referred to collectively as the valinomycin class of antibiotics. A second class of transport-mediating antibiotics, including nigericin dianemycin, and others, has been found to reverse transport induced by the valinomycin class."1-'4 All members of the second class possess low molecular weights (450-950), and lipid solubility, and contain an ionizable carboxyl group.'4 This communication will establish that both classes of antibiotics act analogously in many respects, both in mitochondria and in a variety of other lipid barrier systems. Methods and Materials.-Multiparameter measurements of rat liver mitochondria and other systems, during antibiotic-induced ion movements, were carried out with the apparatus described in detail previously.'5 K+ was monitored with the Beckman 39047 electrode, 02 by a Clark-type membrane electrode, pH by the A. H. Thomas 4858 combination electrode, fluorescence by 450-ma light excited by a 366-mn beam, and light-scattering at 650 mis. Mitochondria were prepared and protein was determined as described previously.'6 Samples of nigericin were obtained from H. A. Lardy, R. Harned (Commercial Solvents Corp.), and M. Gorman (Eli Lilly Co.), dianemycin from Lardy and Gorman, oligomycin from F. M. Strong, and p-trifluoromethoxy arboxylcyanide phenylhydrazone (FCCP) from P. Heytler (duPont). Valinomycin was prepared by means of a Streptomyces culture donated by J. C. McDonald according to a modification of his procedure.'7 Results.-The responses of mitochondria to valinomycin addition as shown in

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Cephalopods and fish have had no common ancestor since the Cambrian, and their eyes are a classic example of convergent evolution. The octopus has no cornea, and immerson renders the trout cornea optically ineffective. As a result, the nearly spherical lens is responsible for all refraction in these eyes. In spite of the fact that the octopus lens consists of two joined parts, while the trout lens consists of one part, we show here that their optical properties are very similar. An index gradient bends rays within these lenses, adding power and correcting spherical aberration. High spherical symmetry in both lenses strongly reduces other monochromatic aberrations and yields a wide field of vision, advantageous in attack and evasion. The octopus Mattheissen's ratio, 2.83, an inverse measure of light-gathering power, lies above the trout value of 2.38 but within the range of values reported for fish. Strong uncorrected longitudinal chromatic aberration is nearly identical in both animals as a result of similar lens protein optical properties, and will limit resolution. We discuss how animal lifestyle requirements and lens material properties influence the design of these eyes.