PREFACE. IX 



jections by Mr, Wallace and Professor Gill to the views there 

 formulated appear in "Natiu'e" of March 22, and June 7, 

 1883, respectively, and my rejoinders to the criticisms of 

 these gentlemen in "Nature " of April 26, and the " Proceed- 

 ings " of the Philadelphia Academy for November, 1883. To 

 these papers I must refer the reader for a purely technical 

 statement of the case. The classification of the " Transition" 

 tracts is largely that which has been proposed by Forsyth 

 Major, in " Kosmos " for 1881. 



Academy of Natukal Sciences, PniLADELrniA, Ocloher, 1SS6. 



