EVIDENCES OF EVOLUTION 33 



complete or striking contrast of aspect and 

 habitat, habit and temperament in the animal 

 kingdom than that between the average bird 

 and the average reptile; and yet every zoolo- 

 gist is sure that birds sprang from some 

 ancient reptilian or saurian stock. He has 

 not ceased to wonder how this transition 

 can have come about; " how the slow, cold- 

 blooded, scaly beast ever became transformed 

 into the quick, hot-blooded, feathered bird, 

 the joy of creation"; but he does not doubt 

 that the transition was effected. He is still 

 unwilling to make any positive statement 

 in regard to the precise pedigree of birds, and 

 yet he is confident that they sprang from a 

 reptilian stock. What are the reasons for 

 this confidence? 



They are threefold : (1) There are, in spite 

 of appearances, numerous structural resem- 

 blances between birds and reptiles, from the 

 scales on the feet to the composition and the 

 articulation of the lower jaw; (2) there are 

 deep similarities in development, for the 

 embryo bird and the embryo reptile travel at 

 first along parallel paths, and only gradually 

 part company; and (3) there are extinct 

 types which to some extent bridge the con- 

 spicuous gap. A word, then, in regard to these 

 connecting links. 



