XXXvVii 
naturalists had found it convenient to assume closer or wider degrees of structural 
affinity as the basis of their classification, derived from the most distinctive character 
of their various groups, of whatever rank. Thus the Mammalia appropriated to the 
land, the birds to the air, and the fishes to the water, were characterized at once by 
the organs which were of the greatest use in enabling them to subsist in their respective 
elements, and hence a primary importance was attached to the organs of locomotion, 
and thus groups were formed and characterized, which have been termed classes, 
orders, families, tribes, genera, &c. It was, however, only upon the greater or less 
degree of resemblance, either of the entire animals or portions of their organs, to 
those which were associated with them in such groups, that these arrangements were 
based. Various kinds of resemblance were, however, accepted by naturalists as 
affording grounds for classification, and while some of these were highly natural, 
others were very artificial in their nature. Species which agreed together in their 
most essential characters were regarded as related together by affinity, but others, 
although bearing a general resemblance, might differ widely in their important 
organisms: this latter relationship, overlookéd by the earlier naturalists, or confounded 
by them with relations of affinity,* was first clearly pointed out by Mr. W. S. 
MacLeay, and in fact formed one of the principal key-stones of his system. Instances 
of this kind of resemblance were then pointed out: 
1. Between members of the different kingdoms of nature: Ex. Byrrhus and a bit 
of earth; the larva of Geometra and a twig; Orcbides and insects. 
2. Between different classes of the same kingdom: Ex. Humming-bird and 
humming-bird moth; eel.and snake. 
3. Between different orders of the same class: Ex. Vespa and Ceria; Trochilium 
and Vespa; Eristalis and Apis; Tricondyla and Condylodera. 
4. Between different sections of an order: Ex. Papilio and Urapteryx; Carabus 
and Adelium. 
_ 5. Between different families of a section: Ex. Papilio paradoxus and Danais; 
Leptalis and Heliconia. 
6. Between different genera of a family: Ex. Species of various genera of 
Heliconiide. 
From the latter instances, the Professor thought it was evident that the relation 
which had been termed mimetic resemblance was only an exaggerated analogy; and 
as these analogies (more or less complete) were found to occur throughout nature it 
might be assumed that they formed an element in creation, and hence that it would be 
unphilosophical and illogical to refer their occurrence in a more striking degree in any 
one instance to a special cause, although the analogy did certainly in many cases 
seem to be given to the creature for purposes of protection. In the MacLeayian and 
Swainsonian systems these analogies were considered as existing as tests of affinities, 
and without regarding or employing them in the sense adopted by the authors of those 
systems, it seemed to Prof. Westwood that it was necessary to take them into con- 
sideration in endeavouring to arrive at a correct view of the general “System of 
* As where Ascalaphus, with its long-knobbed antenna, was described as a 
Papilio. 
