212 ON SYSTEMATIC ZOOLOGY. 



by a totally different process of investigation, arrived 

 at the same general result ; but with this difference, — that 

 he discovered properties, which belonged to this series, 

 of universal prevalence in natural groups, and he deter- 

 mined several of those laws which regulated the variation 

 of animals ; a process of induction which heretofore 

 had never been dreamed of. These discoveries let in 

 a flood of light on the study of nature, and converted 

 that which hitherto had been a science of observation 

 into one of the deepest philosophy. In such a new and 

 untrodden field, it would have been strange indeed, if 

 subsequent researches had not detected errors. Our 

 surprise, therefore, is, not that this theory should be 

 partially defective, but that it should develope so much 

 that is to endure so long as science is cultivated. The 

 system of Mr. MacLeay is eminently natural ; although, 

 as he himself repeatedly declares, it does not claim to 

 be the natural system ; meaning thereby, we may pre- 

 sume, that many principles of that system, and many 

 properties of natural groups, were unknown to him. 

 This admission, on the part of the master, should be 

 borne in mind, when reading the commentaries of his 

 disciples ; for it has unfortunately happened in this, as 

 in other instances, that the reputation of this eminent 

 naturaUst has suffered much more from the zeal of his 

 admirers than from the hostility of his adversaries. On 

 a careful consideration, therefore, of the principles of 

 natural arrangement developed by our author, they may 

 be all comprised under one or other of the following : — 

 1. The demonstration of the circular nature of affinities 

 in natural groups ; 2. The component parts of every 

 group being regulated, in their variation, by some de- 

 finite number ; and, 3. The system of representation, by 

 ■which the contents of one natural group are represented 

 analogically by the contents of other groups. This 

 last ^w, indeed, was not suspected to be universal ; but 

 merely confined to one in every fifth group. The 

 theory of analogy and affinity comes also under this 

 latter head ; being, in fact, one of the tests or proofs to 



