THE POUCHED ANIMALS AS ANCESTORS OF MAN. 153 



attains the height of a man, the embryo develops in the 

 uterus but for a month ; it is then born in a very incomplete 

 condition, and attains all its further development in the 

 mother's pouch, where, for about nine months, it remains 

 attached to the milk-glands. 



All these and other characters ^especially the peculiar 

 structure of the internal and external sexual organs of the 

 male and female) clearly show that the whole sub-class of 

 the Pouched Animals (Marsupialia') are a single group, 

 which originated from the promammalian branch. From a 

 branch of these Pouched Animals (perhaps from several 

 branches) the parent-forms of the higher Mammals, the 

 Placental Animals, afterwards sprang. Hence we must 

 reckon a whole series of Pouched Animals among the an- 

 cestors of the human race ; and these constitute the seven- 

 teenth stage in the human pedigree. 158 



The remaining stages of our ancestral line, from the 

 eighteenth to the twenty-second, all belong to the group of 

 Placental Animals (Placentalia). This very highly de- 

 veloped group of Mammals, the third and last, came into 

 the world at a considerably later period. No single known 

 fossil, belonging to any portion of the Secondary or Meso- 

 lithic Epoch, can be referred with certainty to a Placental 

 Animal, while we have plenty of placental fossils dating 

 from everj part of the Tertiary or Csenolithic Epoch. From 

 this palfeontological fact we may provisionally infer that the 

 third and last main division of Mammals did not develop 

 from the Pouched Animals until the beginning of the 

 Oaenolithic Epoch, or, at the earliest, till the close of the 

 Mesolithic Epoch (during the Chalk Period). In our survey 

 of geological formations and periods (pp. 12, 19) we found 



