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POPULAR SCIENCE REVIEW. 
leaf. The superficial resemblance is occasionally so close, and 
carried into such marvellously minute details of structure, that 
even the eyes of practised entomologists are deceived, as it is 
supposed those of the natural enemies of the animal are. 
Two explanations, and two only, have been offered of the 
origin of this “ mimetism,” or “ protective resemblance ” : — 
natural selection and hybridisation. Mr. Darwin, Mr. Wallace, 
and Mr. Bates advocate the former view, maintaining that the 
resemblance is brought about by exceedingly slow gradations, 
each small variation in the direction of the species ultimately 
mimicked being perpetuated to the prejudice of the offspring 
which do not thus vary, by the operation of the law of 66 The 
Survival of the Fittest.” This theory commends itself, on its 
first enunciation, from its beauty and simplicity, and has been 
eagerly adopted and zealously defended by the ultra-Darwinians 
who form the bulk of our rising naturalists. That this expla- 
nation is, however, not so free from difficulty as its advocates 
have imagined, has been shown by several recent writers, and 
especially by Mr. Mivart in his very able “ Gfenesis of Species,” 
although he has not offered any definite counter-hypothesis. 
The theory of hybridisation has found an advocate in one 
able and experienced naturalist, Mr. Andrew Murray, but has 
not met with general acceptance, and, in addition to other 
objections, is obviously inapplicable, at all events, to the cases 
of the imitation by animals of inorganic forms. 
That similar curious resemblances have not hitherto been 
described in the vegetable kingdom, is mainly because they 
have not been looked for with the same zeal ; and no doubt 
also arises partly from the much greater difficulty of preserving 
the outward appearance of plants than of animals. The exte- 
rior covering of most animals, and in the case of insects the 
whole of the body, is comparatively easily preserved, without 
loss of colour or form, in museums or cabinets. We have no 
such method of preserving the tenderer parts of plants ; and, 
with respect to the colour and form of the natives of tropical 
or unexplored regions, have to trust greatly to the very unre- 
liable fidelity of artists, very few of whom have any accurate 
scientific knowledge. Since, therefore, the most remarkable 
developments of both animal and plant life occur in the wild 
luxuriance of tropical countries, it is only the few who have 
had the good fortune to travel in those regions who have much 
practical opportunity of studying the phenomena we are dis- 
cussing, except in the case of the few species that have been 
cultivated in Europe. The only work that has come under my 
notice in which the subject is discussed, is a little book pub- 
lished in 1869, by Mr. L. H. Grindon, entitled “Echoes in 
Plant and Flower Life,” and he has avowedly not treated it in 
