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 protec- 
tive mimicry, and his work, which was published 
in 1908, may be taken as the latest Neo-Dar- 
winian 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 selec- 
tion 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 re- 
semblances. 
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 
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