To properly comprehend and appreciate mam- 

 mals and their relation to the past, it is necessary to 

 become acquainted with the salient facts of Paleon- 

 tology, Embryology, Anatomy, and Geographical Dis- 

 tribution. The word development or "Evolution" 

 implies change and, since the changes are so slow as to 

 be imperceptible, it is not easy for the uninformed in- 

 dividual to comprehend the changes that have, and are 

 still, taking place, or, to understand the efifects of these 

 changes upon existing life. 



The mammal has its origin in the form of a fer- 

 tilized egg which develops into an Embryo within the 

 body of the mother. The embryo remains within the 

 body and undergoes a further development until the 

 new animal has attained all of its organs and struc- 

 tures and until all of the vital processes are differen- 

 tiated. The length of time for this development within 

 the mother depends upon the kind of animal, varying 

 from three weeks in the rat to almost two years in the 

 elephant. 



As the embryo develops, it passes through an in- 

 teresting series of stages which show, to a remarkable 

 degree, the stages through which the whole race has 

 passed. This embryological development coincides 

 pretty well with the Paleontological evidence, or the 

 fossil records of the evolution of living things. 



The Student of mammals will soon observe th:it 

 there is a unique distribution of animals over the face 

 of the earth. While it is obvious that the faunas 

 of the various continents are characteristic of those con- 

 tinents, it is also just as obvious that many animnl 

 groups in continents which are somewhat removed 

 from one another, are similar in many respects. How 

 may we account for these relationships? 



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