natural conditions;[1] whereas we should think not of years but of geological epochs, for time is only an imaginary quantity, alike useful to the mathematician and historian, a result of expressing the term of our short lives. Thus we may seek to multiply the years of our fugitive existence into a product which shall represent the limits of an unknown past, whilst we can only imagine space by the equivalent of time.
We have already ventured some suggestions on the subject of assimilative colouration, and we now approach a different class of phenomena, where the resemblance is not of colour alone, but also frequently of structure, by which animals exhibit a close resemblance to some inanimate object, and to which the term "Protective Imitation of Particular Objects" has been aptly proposed by Mr. Wallace.[2] One of the most striking examples is found in the Orthopterous family Phasmidæ,[3] and in what are generally known as the "Walking-stick insects." To use the graphic and accurate description of Mr. Wallace:—"Some of these are a foot long, and as thick as one's finger, and their whole colouring, form, rugosity, and the arrangement of the head, legs, and antennæ, are such as to render them absolutely identical in appearance with dead sticks. They hang loosely about shrubs in the forest, and have the extraordinary habit of stretching out their legs unsymmetrically, so as to render the deception more
- ↑ Mr. Sedgwick is of opinion that there is much to be said for the view that the greater part of evolutionary change had already taken place in pre-Cambrian times before the fossiliferous period. "If this view was correct—and the probability of it should be borne in mind—the main part of the evolution of organisms must have taken place under totally different conditions to those now existing, and must remain for ever unknown to us." (Proc. Fourth Internat. Congr. Zoology, Cambridge, 1898, p. 75.)
- ↑ 'Darwinism,' p. 202.—Mr. Skertchley distinguishes "protective resemblance" as copying stationary objects, and "mimicry" as simulating moving ones (Ann. & Mag. Nat. Hist. ser. vi. vol. iii. p. 478).
- ↑ Some Phasmas vary in colour in the same species, as noticed in Mauritius. Cuvier was not unobservant of these peculiarities, as, referring to the Phasma rossia, from the South of France, he describes it as either of a yellow-green or greyish brown. (Quoted by Nicholas Pike, 'Sub-Tropical Rambles,' p. 164.) It is interesting to note a superficial parallelism in structure in the Skeleton-Shrimps (Caprellidæ) with the Phasmidæ, and in Mantis-Shrimps (Stomatopoda) with the Mantidæ, of which a good example may be found in the Squilla mantis, Rondel.
