538 



THE AM ERIC AX NATURALIST 



[Vol. XL. 



court destruction like Darius (xreen, th()U«rli uiany animals which 

 With the exce])tion of the Aniphihia, every class of vertebrates 



tanr. are tiii;luless forms. In true Hiers, however, there is in each 

 instance so distinct a plan of structure that there is not the .slightest 

 doui)t tliat each has arisen tiirough a separate evolution. 



It is nccessurv to (haw a .sharp line of demarcation bet 

 soarers and tliosc having' true flight, and the latter are again 



uhirh ri-e .InwK, l>ut v in thf air ^n.rai'n thnnM-ho ..n almost 



hniited auir.-xpanM' :,n<l inu.t make u..,m1 thi. ill In a ,a;,i 1 xibra- 

 thonuh inchidin- nian> hn-.-'l.ird. nf ^rrnt ^pr.-d .-.^ thr ^^\u\'^..^^v. 



