SUCCESSION AND DEVELOPMENT OF ANIMALS. 175 



their whole organization early stages of the growth of higher 

 representatives of the same type, and embryonic features 

 prevailing more or less extensively in the characters of 

 allied genera, as in the case of the Mastodon and Ele- 

 phant, and what I would call liypeinbryonic types, in 

 which embryonic features are developed to extremes in 

 the further periods of growth, as, for instance, the wings 

 of the Bats, which exhibit the embryonic character of a 

 webbed hand, as all Mammalia have it at first, but here 

 grown out and developed into an organ of flight, or 

 assuming in other families the shape of a fin, as in the 

 Whale, or the Sea-turtle, in which the close connection of 

 the fingers is carried out to another extreme. 



Without entering into further details upon this subject, 

 which will be fully illustrated in my Contributions to the 

 Natural History of the United States, enough has already 

 been said to show that the leading thought which runs 

 through the succession of all organized beings in past 

 ages is manifested again in new combinations in the 

 phases of the development of the living representatives of 

 these different types. It exhibits everywhere the working 

 of the same creative Mind, through all times, and upon 

 the whole surface of the globe. 



SECTION XXVI. 



PROPHETIC TYPES AMONG ANIMALS. 



We have seen in the preceding Section, how the em- 

 bryonic conditions of higher representatives of certain 

 types, called into existence at a later time, are typified, 

 as it were, in representatives of the same types which 

 have existed at an earlier period. These relations, now 



