[24] If the reader happen to be unacquainted with the terms which I have used in characterizing the mouth, he will find them accurately and elaborately described in _Ind. to Ent._ Vol. III. p. 393, _et seq._ The orders of Fabricius depend entirely on the formation of the mouth. See _Systema Entomologiæ_. A second fancy which I wish to combat is, that of analogy and affinity; and as Mr. MacLeay is by far the most learned and competent advocate of these distinct descriptions of resemblance, and as I cannot pretend to refer to or cope with the voluminous writings extant on this subject, I am necessitated to allude to his work alone. It will be seen by the _Horæ Entomologicæ_, (a work which I have already spoken of with unfeigned admiration,) that Mr. MacLeay considers that relation observable in the general appearance, habit, food, metamorphosis, &c. of insects, a relation of analogy, while that dependent solely on a fancied resemblance in the mouth he considers a relation of affinity: thus classes V. and VI., which, in five characters out of six, agree as closely as such comprehensive classes can do, he considers related by analogy, and classes I. and VI., which, in five characters out of six, are as unlike as insects can be, he considers related by affinity;[25] so Dr. Johnson, when he calls affinity "resemblance," must have made a capital blunder, for Mr. MacLeay proves clearly that it means dissimilarity. Classes I. and VI. however, I find will meet as the line becomes bent into a circle, and therefore we must conclude it to be a hidden affinity, for it certainly is not apparent; and moreover it must be remarked, that the relation between classes is but little apparent generally, except they are taken in pairs: thus, between I. and II., between III. and IV., and between V. and VI., the relation is real and readily ascertained, although distant; while between II. and III., between IV. and V., and between VI. and I., it becomes scarcely traceable. It is also worthy of notice, that the contents of either pair of classes, with the addition of class VII., may be formed into a tolerably perfect chain of genera, indeed with much less appearance of disconnexion than is observable on passing from either pair into the next pair,--a fact which attaches a degree of importance to the number three, on which, perhaps, at a future time, more may be said,--and thus a chain of relation would be established in each instance, leaving four whole classes entirely out of the question;--a chain which would steadily pursue its way, regardless and in open violation of all established laws of analogy, affinity and dichotomy; laws which I hope ere long to see pining away like Echo, until they also are really what I now fully believe them to be, _vox et præterea nihil_. [25] Horæ Entomologicæ, p. 367.