INTERNAL AND EXTERNAL AFFINITIES. 233 



Thus,, if we spoke of the relation which the bat has to 

 a bird, we should term it an analogy ; because between 

 the two there is a vast number of intervening groups, 

 but, if we compare the Ornithorhynchus with a bird, the 

 resemblance is an affinity, inasmuch as no quadruped 

 yet discovered shows such a decided tendency to con- 

 nect these two classes of animals. The foregoing ob- 

 servations may be considered as a recapitulation only of 

 what has already been stated of these relations generally. 

 We must now proceed to a more detailed explanation of 

 the relations of affinity than has hitherto been given. 



(286.) Every object in nature has three distinct re- 

 lations of affinity : one, by which it is connected with 

 that object which precedes it in the scale of being ; an- 

 other, by which it is united to that which follows it ; 

 and a third, which connects it to some other object 

 placed out of its own proper circle. That these may 

 be expressed with precision, we term the first two sim- 

 ple or internal affinities, and the latter external. 



(287-) Simple or internal affinities must exist under 

 any system which notices the progression of nature, 

 whether the series be represented as simply linear, or 

 circular : they are not, therefore, peculiar to the latter 

 theory. The dog, for instance, is intermediate between 

 the fox and the wolf; it has, consequently, two direct 

 affinities. 



(288.) External affinities are not always so obvious 

 as the former, except in those aberrant groups which 

 connect two different circles ; for it is manifest that if 

 this third sort of affinity did not exist, the two circles 

 would not blend into each other, as we see they do in 

 nature. But in groups which are unusually abundant 

 in species and in slight modifications of form, there is 

 reason to believe that these external affinities will be 

 found both in typical and aberrant circles. To give an 

 instance of this. The annexed diagram explains the 

 connection of two families, the shrikes (Laniades), and 

 the thrushes (JMeruladcR). Each of these is a circular 

 group, their subdivisions perfectly representing each 



