HAS EVOLUTION REACHED ITS GOAL? 109 



be asked and answered in exclusive reference to the 

 animal stem. The future evolution of vegetable life 

 is, no doubt, a matter of deep interest ; but it is not 

 to be named, for either practical or philosophic im- 

 portance, beside that which we are now to discuss. 



If, then, we contemplate animal life as a whole, 

 and with an eye directed to physical characters less 

 for themselves than for their relation to mental 

 characters, we find that we may make a broad and 

 simple classification. In general terms, animals are 

 either invertebrate or vertebrate. 1 Now from the 

 supreme point of view of mind, the vertebrate may 



1 At this point a somewhat lengthy footnote is indispensable. 

 Were this little volume concerned with organic evolution for itself 

 alone, rather than organic evolution as an indispensable study in 

 preparation for that of mind, society, and morality, it would have 

 been necessary to devote much consideration to that great stage in 

 the process which was marked by the appearance of back-boned 

 animals. Only the stage marked by the appearance of many-celled, 

 as against one-celled, organisms, and that marked by the appear- 

 ance of man himself, can rival or exceed the importance that must 

 be attached to the evolution of the vertebrates. Now it can be 

 shown that this was a gradual process. The older and more familiar 

 terms, vertebrate and invertebrate, are desirably replaced by the 

 terms chordata and achordata. All vertebral columns are preceded, 

 in the history of the individual, by the formation of a structure 

 called the notochord, around which, in the higher forms, the 

 vertebral column and skull are developed. But, from the point of 

 view of what Goethe first called morphology (the science of form), 

 it matters not whether the notochord persists or is later replaced 

 by a spinal column. Hence all animals that have a temporary or 

 permanent notochord are called chordata, whilst those that have not 

 are called achordata. The convenience and justice of the newer 

 terminology is apparent when we find that there are various inter- 

 mediate, worm-like forms, represented even to-day, which have a 

 partially developed notochord — " half " a notochord ; and these we 

 call the hemichordata. Their study has abundantly demonstrated 

 a most important link in the chain of organic evolution. 



