INTRODUCTION 33 
“T. That every natural series of beings, in its progress from a given point, either 
actually returns, or evinces a tendency to return, again to that point, thereby 
forming a circle. 
“Tf. The primary circular divisions of every group are three actually, or five 
apparently. 
“JII. The contents of such a circular group are symbolically (or analogically) 
represented by the contents of all other circles in the animal kingdom. 
“TV. That these primary divisions of every group are characterized by definite 
peculiarities of form, structure and economy, which, under diversified modifications, 
are uniform throughout the animal kingdom, and are therefore to be regarded as the 
PRIMARY TYPES OF NATURE. 
“Vv. That the different ranks or degrees of circular groups exhibited in the 
animal kingdom are NINE in number, each being involved within the other.” 
Though, as above stated, the theory thus promulgated owed its 
temporary success chiefly to the extraordinary assurance and pertinacity 
with which it was urged upon a public generally incapable of under- 
standing what it meant, that it received some support from men of 
science must be admitted. A “circular system” was advocated by the 
eminent botanist Fries, and the views of Macleay met with the partial 
approbation of the celebrated entomologist Kirby, while at least as much 
may be said of the imaginative Oken, whose mysticism far surpassed that 
of the Quinarians. But it is obvious to every one who nowadays in- 
dulges in the profitless pastime of studying their writings that, as a 
whole, they failed in grasping the essential difference between homology 
(or “affinity,” as they generally termed it) and analogy (which is only a 
learned name for an uncertain kind of resemblance)—though this differ- 
ence had been fully understood and set forth by Aristotle himself—and, 
moreover, that in seeking for analogies on which to base their foregone 
conclusions they were often put to hard shifts. Another singular fact is 
that they often seemed to be totally unaware of the tendency if not the 
meaning of some of their own expressions; thus Macleay could write, 
and doubtless in perfect good faith (Trans. Linn. Soc. xvi. p. 9, note), 
“Naturalists have nothing to do with mysticism, and but little with 
@ priort reasoning.” Yet his followers, if not he himself, were ever 
making use of- language in the highest degree metaphorical, and were 
always explaining facts in accordance with preconceived opinions. 
Fleming, already the author of a harmless and extremely orthodox 
Philosophy of Zoology, pointed out in 1829 in the Quarterly Review 
(xli. pp. 302-327) some of the fallacies of Macleay’s method, and in 
return provoked from him a reply, in the form of a letter addressed to 
Vigors On the Dying Struggle of the Dichotomous System, couched in lan- 
guage the force of which no one even at the present day can deny, 
though to the modern naturalist its invective power contrasts ludicrously 
with the strength of its ratiocination. But, confining ourselves to what 
is here our special business, it is to be remarked that perhaps the heaviest 
blow dealt at these strange doctrines was that delivered by Rennie, who, 
in an edition of Montagw’s Ornithological Dictionary (pp. xxxiii.-lv.), 
published in 1831 and again issued in 18338, attacked the Quinary 
System, and especially its application to Ornithology by Vigors and 
Swainson, in a way that might perhaps have demolished it, had not the 
author mingled with his undoubtedly sound reasoning much that is 
