ILLUSTRATIVE OF NATURAL SELECTION. 139 



its name, the possession of mammary glands and the 

 power of suckling the young. What more reasonable, 

 apparently, than to argue that the group in which 

 this important function is most developed, that in 

 which the young are most dependent upon it, and 

 for the longest period, must be the highest in the 

 Mammalian scale of organization? Yet this group is 

 the Marsupial, in which the young commence suckling 

 in a foetal condition, and continue to do so till they 

 are fully developed, and are therefore for a long time 

 absolutely dependent on this mode of nourishment. 



These examples, I think, demonstrate that we can- 

 not settle the rank of a group by a consideration of 

 the degree in which certain characters resemble or 

 differ from those in what is admitted to be a lower 

 group ; and they also show that the highest group of 

 a class may be more closely connected to one of the 

 lowest, than some other groups which have developed 

 laterally and diverged farther from the parent type, 

 but which yet, owing to want of balance or too great 

 specialization in their structure, have never reached 

 a high grade of organization. The Quadrumana afford 

 a very valuable illustration, because, owing to their 

 undoubted affinity with man, we feel certain that they 

 are really higher than any other order of Mammalia, 

 while at the same time they are more distinctly allied 

 to the lowest groups than many others. The case of 

 the PapilionidaB seems to me so exactly parallel to 

 this, that, while I admit all the proofs of affinity 

 with the undoubtedly lower groups of Hesperidse and 



