96 EVOLUTION 



become impure, and a climax of vital activity 

 is attained. The story of the evolution of 

 Invertebrates is a succession of great achieve- 

 ments. Among Vertebrates they were even 

 greater. 



THE ACCENT OF VERTEBRATES. It is a 

 profitable exercise to draw a long ascending 

 slope, with perpendiculars dropped from 

 various points to the base line, registering the 

 evolutionary ascent of Vertebrate animals. 

 What are the impressive facts? (1) Life has , 

 been creeping or pressing upwards for many 

 millions of years. (2) Great specializations 

 occur at eyeyy 1^vel f but there is also beyond 

 doubt ftjrogrf^ive differentiation a H jV 

 tfgra.t.iQji. (3) This is particularly true of 

 the nervous system, and is of course a 

 condition and expression of the gradual in- 

 crease of intelligent behaviour. Life becomes 

 richer and freer. (4) Increased indiy^duation 

 makes reproduci;iye,ef)oi|^]j|y possfofe __ t Pa- 

 i^gntal care increases, an^ the rm^frpr of off- 

 spring^ decreases . TherLis. n .8jQL u eEq^rg^nce of 

 and fondness is sublimed 



--- 



in love. (5) There has been an interesting 

 peopling of the earth, an establishment of 

 faunas distinctive of the shore, the open sea, 

 the deep sea, the fresh waters, and the air. 

 jm,flrk the import* transition 



from water to dry..laq4: the ancient Ptero- 



