It is thus seen that there are many devices by which birds’ eggs are protected, and these have all been developed through the agency of Natural Selection. For example, those exposed eggs of timid birds that varied most in the direction of protectively colored ones were the ones that were most likely to be overlooked by egg-eating creatures, and those that were least protectively colored, and therefore the most conspicuous, were the ones most likely to be destroyed. The protectively colored eggs being thus, in the nature of things, the ones that have suffered less destruction from enemies, have developed into birds that have transmitted, by heredity, their characteristics to succeeding generations of birds’ eggs. And thus in the course of time have many of the colorations of eggs been developed from simple to elaborate patterns. Many snakes, frogs, butterflies, caterpillars, and so on, are colored green in harmony with the foliage of the trees among which they live. By being colored green these animals are more or less effectually hidden from their enemies, such as carnivorous birds. If they were not concealed by protective coloration they would quickly be exterminated by hungry and greedy enemies. The green frogs are greatly protected by their colors from their enemies, the green snakes. If they were not so colored, they would quickly be exterminated by these snakes. Even protectively colored as they are, large numbers of them are caught by the snakes, which are also protectively colored and keener witted. It may be stated that the protectively colored frogs are hunting for their food, the protectively colored insects; but, at the same time, they try to avoid their protectively colored enemies, the snakes, though they are often caught; the protectively colored snakes are hunting for their food, the frogs, but, in their green surroundings, endeavor to avoid their enemies, the reptile-eating birds, though often unsuccessful. And so on, from day to day, the tragedies of the animal world are enacted.