290 THE HISTORY OF CREATION. 



ance, be admitted to be the descendants of a single common 

 primary form, namely, of the Protanujipn. 



Sixteenth Stage : Primary Mammals (Fromammalia), 



We now find ourselves more at bome with our ancestors. 

 From the sixteenth up to the twenty-second stage they 

 all belong to the large and weU known class of Mammals, 

 the confines of which we ourselves have as yet not 

 transgressed. The common, long since extinct and unknown 

 primary forms of all Mammalia, which we have named 

 Promammalia, were at all events, of aU still living animals, 

 of the class most closely related to the Beaked animals, or 

 Ornithostoma (Ornithorhynchus, Echidna, p. 233). They 

 differed from the latter, however, by the teeth present 

 in their jaws. The formation of the beak in the Beaked 

 animals of the present day must be looked upon as an 

 adaptive characteristic which developed at a later period. 

 The Promammalia arose out of the Protamnia (probably 

 only at the beginning of the secondary period, namely, in 

 the Trias) by various advances in their internal organis- 

 ation, as also by the transformation of the epidermal scales 

 into hairs, and by the formation of a mammary gland 

 which furnished milk for the nourishment of the yovmg 

 ones. The certain proof that the Promammalia — inasmuch 

 as they are the common primary forms of all Mammals — 

 also belong to our ancestors, lies in the comparative 

 anatomy and the ontogeny of Mammalia and Man. 



Seventeenth Stage : Pouched Animals (Marsnpialia). 



The three sub-classes of Mammalia — as we have already 

 seen — stand in such a rela,tion to one another that the 



