In other cases the mimicry of the dry-weather form is said to be far more perfect.
Instances of this phenomenon are set forth in Professor Poulton’s Essays on Evolution.
Alternative Theories
It will be observed that we have quoted very largely from Professor Poulton’s work. Our reason for so doing is that he appears to be the most prominent advocate of the theory of protective mimicry, and his work, which was published in 1908, may be taken as the latest Neo-Darwinian pronouncement on the subject.
Hence if we can show, as we believe we can, that his arguments are not sound, we may take it that we have demonstrated that the theory in its present form is untenable.
It is worthy of notice that Professor Poulton sets forth three other suggestions which have been proposed as substitutes for natural selection as an explanation of the phenomena of mimicry.
The first is the theory of External Causes, namely, that the resemblance is due to some external cause, such as food or climate.
The second is the theory of Internal Causes, which states that mimetic resemblance is due to internal developmental causes.
The third is the suggestion that sexual selection has caused the origin of these resemblances.
He then proceeds to demolish these to his own satisfaction, and adds triumphantly, “The conclusion appears inevitable that under no theory, except natural selection, do the various resemblances of animals to their organic and inorganic environments fall together into a natural arrangement and receive a common explanation” (p. 228).