SCIENCE 



NEW YORK, JUNE 16, 1893. 



ORGANIC COLOR. 



BT F. T. MOTT, F.R G.S , LEICESTER, ENGLAND. 



The colors of plants and animals may be due (1) to diffraction 

 and interference from striated surfaces, as in some iridescent 

 feathers and shells; or (3) to pigments whose function seems to be 

 especially to give color ; or (3) to the molecular structure of the 

 tissues themselves. 



The first of these causes is not a physiological phenomenon. It 

 can be equally well exhibited by artificial means. The second 

 and third are phenomena connected with the most fundamental 

 elements of organic life. 



The colors of tissues or pigments depend, of course, upon the 

 portion of white light which is reflected from them. The white 

 light of the sun falling upon an object is in all cases partly 

 absorbed and partly reflected. This " light " is merely a series of 

 undulations or ripples running through the ether, the ripples being 

 of various sizes; and the color of the object depends altogether 

 upon the quantity and the size of the ripples which are stopped or 

 absorbed. The cause of the difi'erences in color among varioas 

 organic objects must lie in the varying power of absorption 

 possessed by the tissues. The petals of a pink rose absorb the 

 undulations of medium size, and reflect both the larger and 

 smaller ones; while the petals of a scarlet geranium absorb the 

 small undulations, reflecting only the medium and larger ones. 

 But -why should this difference exist in the absorbing power of 

 the flowers? 



Here is the crux, which is still a crux in spite of the mucb- 

 lauded hypothesis of insect selection. Insect selection may ac- 

 count for something, but there is much more for the explanation 

 of which it is quite unavailable. The supposed all-sufficiency of 

 this hypothesis is completely answered by the fact that insect 

 selection cannot come into play at all in the production of color 

 until the plant has already shown its power to produce that par- 

 ticular color quite independently of insects It is evident that 

 the color is due not to insects, but to some inherent capacity of 

 the plant, and that a plant which could produce a small pink 

 petal could equally well produce a large one under suitable con- 

 ditions. The utmost that can be claimed for insect selection is 

 that it may accelerate the production of the large and showy 

 petals by giving to the plants which show their tendency to pro- 

 duce such petals better opportunities of developing that tendency. 

 The crucial question remains. What is it which gives to a plant 

 this tendency to produce colored petals? 



There are two fundamental laws of nature which, in the 

 attempts to solve this question, have not been sufficiently regarded, 

 viz., (1) the law of the concentrating wave, and (2) the law of 

 sympathetic vibration. By studying the action of these laws, it 

 seems possible to carry the solution at least one step further back 

 from the position in which it now stands. 



We are familiar with the simple wave of oscillation, as in the 

 pendulum; and also with the wave of undulation, as in sound, 

 light, and the spreading rings upon the surface of water; but 

 the wave of concentration is less familiar to us, and has been less 

 carefully studied. 



All organisms are illustrations of this particular wave-form. 

 As the kinetic energy of the swinging pendulum increases as it 

 approaches the centre of its curve, and then again diminishes, so 

 the energy of the organism increases as it approaches the climax 

 of its life, and then diminishes. But, while the swing of the 

 pendulum is a simple process, involving merely the alternate 

 change of form of a given amount of energy, the growth of an 



organism is almost infinitely complex. The accumulation of en- 

 ergy which this growth represents takes place slowly and inter- 

 mittently by the drawing-in of outlying units to a centre, the en- 

 ergies of these units being aggregated and assimilated to the forma 

 of the original germ. This accumulation of energy continues, if not 

 violently interrupted, until a certain deSnite degree of concentra- 

 tion is attained, after which a gradual dispersion of the energy 

 sets in until the organism dies of old age. All organic individ- 

 uals have a limited period of life, and pass through a similar series 

 of periodic changes, gradually attaining a cHmax of concentrated 

 energy, which is afterwards gradually dissipated. The ascending 

 and descending phases of the wave are rarely equal, but probably 

 always equivalent. One may be long and slow, the other short 

 and rapid, or vice versa. The variations in this equivalence may 

 be almost infinite. 



It is clear that this law of the concentrating wave controls the 

 life-history of every individual. It is not so demonstrable, but 

 is, nevertheless, highly probable that the same law controls the 

 development of species, genus, order, and class, and is, in fact, 

 the fundamental law of the unfolding universe, at all events, of 

 the organic phase of it. 



What is the relation of this law to organic color? 



Let us assume the general correctness of the molecular theory 

 as the nearest approach which science has yet made to an explana- 

 tion of the structure of matter. 



Throughout all substances in which the temperature is above 

 the point of absolute zero, as in all living organic substances, the 

 molecules must be in continual motion. But, being linked to- 

 gether by powerful ■' affinities " (whatever these may be) into defi- 

 nite groups, and in all solid bodies packed very closely together, 

 their motions cannot be altogether free. There must be certain 

 directions in which they ran move, and certain others in which 

 they cannot move; and the group of motions possible to them 

 will differ in each compound chemical substance. There wiU be 

 a definite group of motions possible to the molecules of albumen, 

 another to those of starch, etc. There will also be a definite but 

 more complex group of motions possible to the totality of mole- 

 cules which make up each kind of tissue, as skin, muscle, bone, 

 nerve, etc., and a still more complex group possible to those which 

 make up each organic individual. This characteristic grouping 

 of possible motions may be called molecular rhythm. 



One of the specific functions of organized matter is that of 

 assimilation and growth. There is no organism which can assim- 

 ilate matter of every kind. The power of selecting food depends 

 upon the molecular rhythm of the organism. Substances whose 

 molecules have possible motions which harmonize with those of 

 the feeding organism can be assimilated and made to add their 

 energies to the stock of that individual, causing it to " grow " in 

 size and in accumulated energy. Substances whose molecular 

 rhythm will not allow of such assimilation are not available as 

 food for that organism. 



The organism continues to feed, to assimilate, and to grow, in 

 accordance with the law of the concentrating wave up to a certain 

 point, but there is a limit which it cannot pass. Having reached 

 that limit, concentration ceases and dispersion sets in. What de- 

 termines that limit? 



The phenomenon of growth is not a passing function, not a mere 

 reception and assimilation of energy. Every organism is more 

 or less active and parts with energy as constantly as it receives it. 

 Growth is the result of the balance between these two processes. 

 As long as the organism assimilates more energy than it dissipates 

 by its various activities, growth continues. 



The limiting-point is that epoch in life at which assimilation 

 becomes so small as to be overtaken by the dispersion. But what 

 diminishes the power of assimilation ? 



