106 ON SYSTEMATIC ZOOLOGY: 
CHAP. III. 
ON NATURAL SYSTEMS. — PRELIMINARY OBSERVATIONS. — DE- 
FINITION OF A NATURAL SYSTEM. — HERMANN’S. — OBSERY= 
ATIONS. — LAMARCK’S SYSTEM OF THE INVERTEBRATED 
ANIMALS. = SYSTEM OF MACLEAY IN ENTOMOLOGY. — 
FRIESS IN BOTANY. — ALTERATIONS IN MACLEAY’S SYSTEM, 
— REMARKS THEREON.— SEPTENARY AND OTHER THEORIES. 
— GENERAL REMARKS ON NUMERICAL THEORIES, AND ON 
THE NECESSITY OF PROVING THAT GROUPS ARE CIRCULAR, 
(253.) Wer have already touched upon the essential 
distinctions between an artificial and a natural system ; 
but the latter will now claim more of our attention. As 
every principle of analogical reasoning, and every result 
of minute investigation, leads to the conclusion that: 
there is a unity of plan throughout that part of creation 
which embraces the animal world, so it follows that 
there cannot, strictly speaking, be more than one na- 
tural system. It may, therefore, be objected to us, as 
it has already been to others, that, by speaking of na- 
tural systems, we imply that there may be several. Let 
us, therefore, at the commencement, be clearly understood 
upon this point. If, by the natural system, we are to 
understand a complete developement of all the properties 
and relations of animated beings; the functions they 
are intended to perform; the principles upon which 
their forms have been regulated ; their indisputable af- 
finities among themselves, and their innumerable ana- 
logies to all others, then the natural system is a pinnacle 
of knowledge te which finite beings can obviously never 
reach. But this, though a just definition, is too theo- 
retical for practical use; seeing that human knowledge 
must be for ever imperfect, while the faculties of the 
