206 ON SYSTEMATIC ZOOLOGY. 
only, which are but five : — “‘ Indeed, when it is consi- 
dered that there were so many affinities to be reconciled 
with this constant use of the number five, it is clearly 
absurd to imagine that I would have hampered myself 
needlessly with such a rule. My sole object has been 
to demonstrate natural affinities ; and in doing this I 
have fallen on a distribution into five groups, so uni- 
formly, that where there seems to be an exception to 
the rule, it appears to be as much the consequence of 
our little acquaintance with the manifold productions of 
nature, as of any other cause whatsoever. No person, 
however, can be more reluctant than I am to make 
any conclusion on this subject precipitately ; and, there- 
fore, in saying that there is a general tendency, in every 
natural group of animals, to be subdivided into five 
others, I would only have this opinion accounted an 
hypothesis, which is not entirely destitute of arguments 
wherewith we may support its truth. Yet I must ac- 
knowledge that it appears to me, even by what we have 
already seen, to be so far established, that, in future, 
where great chasms occur in smaller groups, I shall con- 
sider myself entitled to suppose that these proceed from 
our ignorance of the productions of nature.” * Upon 
the whole, therefore, we are justified in concluding that 
our author believes some groups to be composed of ten 
circles, and others of five, or, what is the same thing, 
that sometimes there are five large groups and five 
smaller ones, and sometimes five only. 
_ (261.) We now come to the fourth principle of 
natural arrangement, pointed out by our author, viz., 
that here is a tendency in such groups as are placed at 
the opposite points of a natural circle to unite. But on 
this intricate subject we will take his own words, and 
his own illustrations of their meaning. For this pur- 
pose let the reader refer to the diagram of the animal 
kingdom, as to a map, while he peruses attentively the 
following passagé:-— ‘‘ On the examination of this 
* Hor. Ent. p. 322, 
