AFFINITIES AND GENEALOGY. 179 



group is diversified and broken to an extraordinary degree, 

 and includes many aberrant forms. It has, therefore, proba- 

 bly suffered much extinction. Most of the remnants sur- 

 vive on islands, such as Madagascar and the Malayan- Archi- 

 pelago, where they have not been exposed to so severe a 

 competition as they would have been on well-stocked con- 

 tinents. This group likewise presents many gradations, 

 leading, as Huxley remarks,* " insensibly from the crown 

 and summit of the animal creation down to creatures 

 from which there is biu a step, as it seems, to the lowest, 

 smallest and the least intelligent of the placental mam- 

 malia." From these various considerations it is probable 

 that the Simiadae were originally developed from the pro- 

 genitors of the existing Lemuridar, and these in their turn 

 from forms standing very low in the mammalian series. 



The Marsupials stand in many important characters 

 below the placental mammals. They appeared at an 

 earlier geological period, and their range was formerly 

 much more extensive than at present. Hence the Placen- 

 tata are generally supposed to have been derived from the 

 Implacentata or Marsupials ; not, however, from forms 

 closely resembling the existing Marsupials, but from their 

 early progenitors. The Monotremata are plainly allied to 

 the Marsupials, forming a third and still lower division in 

 the great mammalian series. They are represented at the 

 present day solely by the Ornithorhynchus and Echidna; 

 and these two forms may be safely considered as relics of a 

 much larger group, representatives of which have been pre- 

 served in Australia, through some favorable concurrence of 

 circumstances. The Monotremata are eminently interesting, 

 as leading in several important points of structure toward 

 the class of reptiles. 



In attempting to trace the genealogy of the mammalia, 

 and therefore of man, lower down in the series, we become 

 involved in greater and greater obscurity; but as a most 

 capable judge, Mr. Parker, has remarked, we have good 

 reason to believe, that no true bird or reptile intervenes in 

 the direct line of descent. He who wishes to see what 

 ingenuity and knowledge can effect, may consult Prol 

 Hackel's works. f I will content myself with a few general 



*" Man's Place in Nature,'' p. 105. 



f Elaborate tables are given in bis ' Genere'.le Morphologic " (B, 

 ii, s. 153 aud s. 425j; and with inure especial reference to mail iu Lia 



