222 THE DESCENT OF MAN. [Part I. 



amount of convergence. This is the case, as shown by 

 Yon Nathusius," -with the improved breeds of pigs, which 

 are descended from two distinct species ; and in a less 

 well-marked manner Avith the improved breeds of cattle. 

 A great anatomist, Gratiolct, maintains tliat the anthro- 

 pomorphous apes do not form a natural sub-group ; but 

 that tlie orang is a highly-developed gibbon or semno- 

 pithecus ; the chimpanzee a highly-developed macacus ; and 

 the gorilla a highly-developed mandrilL If this conclu- 

 sion, which rests almost exclusively on brain-characters, 

 be admitted, we should have a case of convergence at 

 least in external characters, for the anthropomorj^hous 

 apes are certainly more like each other in many points 

 than they are to other apes. All analogical resemblances, 

 as of a whale to a fish, may indeed be said to be cases of 

 convergence ; but this term has never been applied to 

 superficial and adaptive resemblances. It would be ex- 

 tremely rash in most cases to attribute to convergence 

 close similarity in many points of structure in bemgs 

 Avliicli had once been widely difierent. The form of a 

 crystal is determined solely by the molecular forces, and 

 it is not surprising that dissimilar substances should some- 

 times assume the same form ; but with organic beings we 

 should bear in mind that the form of each depends on an 

 infinitude of complex relations, namely, on the variations 

 which have arisen, these being due to causes far too intri- 

 cate to be followed out — on the nature of the variations 

 which have been preserved, and this depends on the sur- 

 rounding physical conditions, and in a still higher degree 

 on the suiTounding organisms with wliich each has come 

 into competition — and lastly, on inheritance (in itself a 

 fluctuating element) from innumerable j^rogenitors, all of 



■^'Dic Racen des Schwcincs,' ISGO, s. 46. 'Vorstudicn fiir Ge- 

 schichtc, etc., Schweineschiidcl,' 18frt, s. 104. 'With respect to cattle, 

 see M. de Quatrcfages, 'Unite de I'Especc Ilumaine,' 1861, p. 119. 



