486 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



natural selection, describing it as the motive cause of mimetic resemblance. 

 Darwin was most careful to point out that it does not " induce variability," 

 but " implies only the preservation of such variations as arise and are 

 beneficial to the being under its conditions of life." It is these " con- 

 ditions " which by their " direct action " give rise, by response on the 

 part of the organism, to "definite results." * Hence to describe natural 

 selection as the " cause " of anything is contrary to Darwin's theory. 



Seasonal changes, not only shown in nature, but by Mr. Marshall's 

 experiments, clearly prove that the conditions of life were the cause, and 

 not natural selection. This is paralleled by more rapid changes in 

 mimetic colours in flat-fish, trout, frogs, and especially the chameleon ; 

 so that probabilities favour Darwin's "cause." A remarkable case is 

 the tropical male Hypolimnas misippus, mimicked in China by 

 Limenitis albomaculata, and also by Athyma punctata — all three are 

 black and white butterflies. " There was, in fact, from the very first, 

 sufficient likeness for Natural Selection to work upon." But surely, 

 udging by all analogy, " similar conditions of life will ensure similar 

 developments " is a sufficient and better explanation than the unproven 

 one of natural selection, which is based on " We may feel sure that any 

 variation in the least degree injurious would be rigidly destroyed." 

 Professor Poulton adds that mimicry is " known by a vast body of 

 observations which receive an intelligible interpretation under this theory, 

 but not under any other." t This may be true if any evidence could be 

 found of " indefinite variations " upon which natural selection is based. 



Professor Poulton truly says : " We believe in evolution, not because 

 we see it taking place, but because of the immense number of observed 

 facts which it renders intelligible ; and the same is true of our confidence 

 in the Newtonian theory." This is a concise description of induction ; 

 but we can see evolution taking place whenever an organism grows up 

 under " changed conditions of life " and adapts itself to them both in 

 nature and cultivation. 



Professor Poulton says : " It is impossible to explain why external 

 forces or internal forces should act upon a certain set of characters 

 whose only relationship is that they tend to produce a superficial 

 likeness to another species." t This is perhaps true for the animal 

 world especially, at present ; so is it impossible to explain how the 

 pitcher of Nepenthes (a hypertrophied water-gland) and that of Cephalotus 

 (a true leaf-blade) have come to be so closely alike ; yet the result of 

 self-adaptation without natural selection is so universally seen in plants 

 that the probability is that exceptional cases will fall into line when more 

 is known about them. 



In conclusion, I will return to the first page and refer to the idea 

 of " confidence " in the theory. This confidence is everywhere observable 

 throughout the book. Every fact is explained by natural selection ; but 

 in no single case does the author supply the necessary conditions as 

 existing, or ever having existed, without which natural selection falls 

 to the ground. Thus Professor Poulton says : " A mimetic appearance 

 is commonly made up of (1) colour, including (a) structural as well as 



* Essays, p. 2 is. + j j0c . ext. p. 237. 



t An. and PL luuler Dom. ii. p. 271 



