Natural Selection is usually spoken of by those who still put it forward for popular consumption in terms of _one_ advantageous difference: for instance, slightly greater speed, slightly better protective colouring, etc. This escape from the difficulty is duly repeated here by Mr. Wells. He gives us, as an example of the way in which Natural Selection would work, the climate becoming more snowy and, of a number of whity-brown animals, the whiter tending to survive in each generation, and the quality of whiteness tending, therefore, to increase. No better instance could be found of the way in which this book merely follows (and repeats) the mistakes of a generation ago. For that instance of the whity-brown animal is the regular old tag which always cropped up whenever this theory of Natural Selection was advanced. It should surely have been evident, even to the originators of the idea (as it is now at last evident to everybody worth counting), that what you need in order to adapt (_a._) an animal to new circumstances, (_b._) any developing function of a particular species, (_c._) the development of many co-ordinated functions within one organism, is not one simple advantage, but _an indefinitely large number of advantages, all of which have to be co-ordinated if survival-value is to be obtained_. When the climate gets colder, there will probably be more snow. But this is not the only thing that will happen. There will also be a change in the methods of progression over the surface of the earth. Paws advantageous for speed when there was no frost or snow may be disadvantageous when there is. There will also be a change in the things present for an animal to eat; many of the grasses and fruits present in the warmer time will presumably disappear and others better suited to the new, cold climate will increase. Again, a change of this kind does not take place in isolated fashion; it will be accompanied perhaps by longer nights in winter; probably by more cloudy skies, and by sudden floods in spring, and so on. Change of environment will nearly always mean not one, but a very great number of concomitant changes. Change, then, in environment is always complex. But the organism which has to meet it is also complex, only because it _is_ an organism. Every living organism is highly complex. It is its very complexity, that is, the vast number of its parts and the mysterious co-ordination between them, which makes it a living organism, and distinguishes it from dead matter. Even the simplest organic cell is chemically of a highly complex nature, and its principle of continuity is so different from a simple mechanical process that no one has ever been able to lay down a formula for it. In plain words, the very nature of a living organism escapes us on account of its complexity.