MIMICRY. 295 



their remains from Mesozoic strata is rather remarkable."* But 

 the difficulties in the clear conception of this question do not end 

 here. As early as this Carboniferous epoch, these insects appear 

 to have possessed what we naturally consider as a protected or 

 imitative structure, and this view is inconceivable without the 

 antecedent proposition that their enemies then existed, and that 

 the imitative guise was that of the oft-devoured against the 

 would-be-devourer. But it is affirmed that Lizards do not 

 appear before the Permian epoch,! birds as certainly not before 

 the Jurassic { or perhaps the Triassic formation. " It is quite 

 possible that birds existed during the Triassic period, but at 

 present there is no proof of it." § And if these facts were taken 

 as final, then an insuperable difficulty would exist as to the 

 structure of these Phasmidce being due to a gradually acquired 

 protective character. But the same argument applies to these 

 ancient Lizards as to our Carboniferous Stick-insects. As 

 Huxley remarks, " These Permian Lizards differ astonishingly 

 little from the Lizards which exist at the present day"; and 

 again, " It is perfectly clear that if our palseontological collections 

 are to be taken, even approximately, as an adequate representa- 

 tion of all the forms of animals that have ever lived, and if the 

 record furnished by the known series of beds of stratified rocks 

 covers the whole series of events which constitute the history of 

 life on the globe, such a fact as this directly contravenes the 

 hypothesis of evolution ; because this hypothesis postulates that 

 the existence of every form must have been preceded by that of 

 some other form different from it." || If we study the records of 



* Scudder, " Syst. Rev. Pres. Knowl. Foss. Ins." (Bull. U.S. Geol. Surv. 

 No. 31, p. 49 (1886)). 



f This seems to be the current statement based on present knowledge ; 

 but, as Huxley has observed, analogy seems to be rather in favour of, 

 than against, the supposition that Amphibia and Reptilia, or even higher 

 forms, may have existed, though we have not yet found them in the Devonian 

 epoch (' Collected Essays,' vol. viii. p. 385). 



I The oldest known bird — Archceopteryx — comes from the Solenhofen 

 Limestone in the Upper Jurassic series — a rock which has been especially 

 prolific in the fauna of the Jurassic period (A. Geikie, ' Text-Book of Geology, 

 2nd edit. p. 783). 



§ 0. C. Marsh, ' Sixteenth Ann. Kept. U.S. Geol. Survey,' p. 147 (1896). 



|| ' Collected Essays,' vol. iv. p. 85. 



