402 ON THE ORDERS 



We shall retum, for this purpose, to the relations of ana- 

 logy visible between the circles of Mandibulata and 

 Ilaustellata, where 1 take it for granted that the two se- 

 ries are perfectly natural according to the foregoing defi- 

 nition, that is, because they are only broken by chasms 

 and not interrupted by unnatural interventions. But it is 

 far from being a necessary consequence of the series being- 

 natural, that the specification of the five orders which com- 

 pose each series should also be correct. I make this re- 

 mark, because a fluctuation of the line of analogy is often 

 visible ; for which I cannot see any sufficient cause unless 

 the circumstance, before noticed, of every external order 

 bearing an analogy to the two external orders of the con- 

 tiguous class, may hereafter prove to be such. As we 

 have heard so much of the distortions and dislocations of 

 natural order, and as so many of these have now disap- 

 peared, it is my firm belief that Natural History scarcely 

 knows what is truly an anomaly. There is, at least, a 

 possibility of these apparent fluctuations being hereafter 

 in like manner reduced to a regular principle. But whe- 

 ther it be owing to the above circumstance, or to some 

 cause of which as yet we have no idea, or whether it re- 

 sults from our orders being badly constructed, the effect 

 is undoubtedly visible. To explain what is ineant: a 

 Dipterous insect resembles a Hymenopterous one in ap- 

 pearance as well as metamorphosis; the genus Pulex also 

 resembles the Coleoptera, and the Lepidoptera imitate the 

 Trichopfera in these same points : consequently, as to the 

 accuracy of the position of three groups in each series there 

 can be no doubt. Yet, although the analogy of meta- 

 morphosis remains unobjectionable, that of external ap- 

 pearance and even of economy appears not to follow 



