16 SCIENTIFIC ILLUSTRATIONS [App 



from their close resemblance to vegetable productions, the names 

 of walking sticlcs and walking leaves are commonly given. Both 

 are remarkable in their appearance. In the walking leaves 

 (Pliylliidce) the body is very flat and thin, and the wings form 

 large, leaf-like organs, covering nearly the whole abdomen, and 

 furnished with irregularly reticulated nervures, which give them 

 exactly the aspect of a leaf. This leafy structure pervades the 

 whole animal; the legs, especially the thighs, being always 

 foliaceous. Some species are of a bright green colour, whilst 

 others are of the brown of dead leaves ; and the natives of the 

 countries inhabited by these curious creatures generally inform 

 Europeans that the insects are all green at first, but that as the 

 leaves change colour they change also. But even amidst the 

 changes still the "things are not what they seem." Take another 

 example illustrating the same principle. It is well enough known 

 that many creatures, formerly supposed to be vegetable, such as 

 the corals and the zoophytes, have since found their proper place 

 in the animal kingdom ; and one consequence of this reforma- 

 tion was, that several real plants were supposed to be animals, 

 because they possessed some of the characteristics which had dis- 

 tinguished those animals that had been placed in their proper 

 position. Of these plants the coralline is a good example, for 

 until a comparatively late period it was placed among the 

 animals in company with the true corals. There was reason 

 for this error, for the coralline is a very curious plant indeed, 

 gathering from the sea-water, and depositing in its own sub- 

 stance so large an amount of carbonate of lime that when the 

 purely vegetable part of the alga dies and is decomposed, the 

 chalky portion remains, retaining the same shape as the entire 

 plant, and very much resembling those zoophytes with which 

 it has been confounded. While growing, the coralline is of a 

 dark purple colour, but when removed from the water the 

 purple tint vanishes, and the white stony skeleton remains. It 

 is, however, a true vegetable, as may be seen by dissolving away 

 the chalky portions in acid; there is then left a vegetable 

 framework precisely like that of other algse belonging to the 

 same sub-class. N. H. & c. 



