142 ON AFFINITY AND ANALOGY. 



cessity of the existence of some kind of relationship founded 

 upon similarity of structure, in order to establish thereon a 

 distribution whereby species are endeavoured to be arranged 

 according to their greater or less similarity of organization, 

 have admitted only one kind of relationship or resemblance, 

 as they have termed it, regarding affinity and analogy as only 

 synonymous with resemblances. 



The first and second classes of these writers may be dis- 

 missed from our notice in a veiy few words. If we admit 

 that there be a system of nature wherein animals are arranged 

 and distributed, we must admit the existence of relations 

 founded upon structural similarities or differences ; and these 

 relations, according to their degree, constitute what have been 

 termed affinity and analogy, the distinctions of which are 

 overlooked by the third class of writers, who however ac- 

 knowledge structural relations or resemblances. 



It appears to me, however, that notwithstanding all that 

 has been said by the supporters of the doctrine of affinity and 

 analogy as distinct relations, not a small share of the miscon- 

 ception which has prevailed upon the subject with professed 

 distributionists, has resulted from the silence of the former 

 concerning what appears to me to be a fundamental principal 

 in the theory, which may be stated as follows. 



Relations of affinity and analogy have their origin in more 

 or less perfect resemblances of structure or habits, and are of 

 comparative and relative value ; and hence that distinct rela- 

 tions, both of affinity and analogy, exist between the same 

 groups. 



Much has been admirably said respecting the immediate 

 and the remote relations of objects, and the differences 

 between their symbolical relationship and their natural affini- 

 nities, whilst at the same time many excellent examples have 

 been given in illustration of their distinctions. Amongst the 

 latter, none have been more striking than that employed by 

 Mr. Swainson in his ' Treatise upon the Natural System of 

 Animals,' illustrating the relation of affinity existing between 

 the swallow and the goat-sucker, and the relation of analogy 

 between these and the bat. 



In applying this example as a practical illustration of the 

 principle above laid down, it will scarcely be deemed neces- 

 sary, in the first place, to enter into any argument to prove 

 that relations of affinity, as well as of analogy, have their ori- 

 gin in more or less complete resemblances of structure or 

 habits : indeed, one of the most strenuous advocates of the 

 doctrine in question, has observed that " every created being 

 has different degrees of relationship or of resemblance to 



