220 OBSERVATIONS UPON THE 



circles, or pentagons. This healthy tone of mind imparts a 

 high value to all that proceeds from Mr. Westwood's pen, 

 and it is, therefore, with much diffidence that I venture to 

 make a few remarks on the short essay above referred to. 



There is no branch of the philosophy of Zoology so ob- 

 scure as the subject of affinity and analogy ; and although 

 many naturalists can correctly apply these two kinds of rela- 

 tions to particular cases, yet few can give any clear explana- 

 tion of the rules which influence their practice. Mr. West- 

 wood's remarks go deeper into the subject than those of most 

 of his predecessors, yet it seems to me that he has not quite 

 set the question in its true light. Before referring to his ob- 

 servations, I will endeavour to explain my own views on this 

 difficult subject. 



Relations of affinity and analogy are in my opinion per- 

 fectly distinct from each other in every point of view. In 

 order to arrive at their definitions, we must first prove the 

 existence of a real natural system, a subject which involves 

 an enquiry into the designs of creative power, one of the 

 most awful themes which the human intellect can attempt. 

 The most obvious and undeniable examples of design in the 

 organised creation are seen in the adaptation of each species 

 to the circumstances in which it lives. Now, if this were the 

 sole mark of design, if each species constituted a being per 

 se, adapted to its peculiar condition of existence, but not 

 allied in physiological structure to its fellow species, there 

 would then be no natural system; — man might indeed clas- 

 sify such objects according to their accidental or fancied 

 resemblances, but there would be none of those essential 

 peculiarities of structure which we find to pervade vast 

 groups of beings whose external forms are often widely dis- 

 similar. The existence then of a comparatively few grand 

 types of structure, or " centres of creation," from the differ- 

 ent modifications of which the innumerable species now 

 existing derive their characters, may be taken as a proof that 

 species were created not absolutely, but relatively, — not 

 merely with reference to their destined mode of life, but also 

 with reference to other species whose destination was similar, 

 though not identical with their own. If these views be cor- 

 rect, it results that the resemblances of different species in 

 essential points of structure, furnish evidences of design, less 

 obvious, perhaps, but not less certain, than the adaptation of 

 any one species to its external condition of existence ; and 

 the " natural system" thus acquires an air of truth not inferior 

 to the ocular demonstrations of anatomy. The reality of the 

 natural system is not affi^cted by the difficulty experienced 



