196 ON SYSTEMATfc ZOOLOGY. 



CHAP. III. 



ON NATURAL STSTEMS. PRELIMINARY OBSERVATIONS. BK- 



riNITION OF A NATURAL SYSTEM. HERMANN'S. OBSERV- 

 ATIONS. — Lamarck's system op the invertebrated 



ANIMALS. SYSTEM OF MACLEAY IN ENTOMOLOGY. 



TRIES'S 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.) We 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 to 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 



