PR EFACE. 



T 1 - common mistake to designate my classification as "embryological." 

 •*- It will 1m- found by those who read these pages, that the whole life 



of the individual, and all its metamorphoses, have 1 n deemed essential 



standards for the estimation of affinities. Even the degradational raeta- 



morpl ss of old age sre used as characteristics of value in the generic 



ns; it is properly speaking an ontological classification. 



conducted almost wholly in Museums, because it 



found impracticable to Btudy Btratigraphical superposition in the field. 



pari of tli" wmk lias already been accurately done by load treolo- 



and my notes were largely made upon their collections .Mute 



extended Btudies might have made the work more accurate than it i<. 



but tl >1 possible for me. 



I desire to record my deep sense of obligation to the late Prof. Louis 

 /. under whose direction my Btudies upon the Arietidaa were begun. 



tion and advi< none the less valuable because we differed 



in theoretical views; to bim I owe the methods of observation wliieli are 

 used in all my work. 



II n, Alexand A - also laid scientific nun in this country 

 under heaw obligations, and this dd not have been completed or 

 published but for his sympathy, and for the liberal manner in which he 



ed by large personal - the collections and th< 



rch in the Museum of Comparative Zoolo 



the Smithsonian Institution, has shown the 



.1 and courtesy, and in undertaking the Bpeedy pub- 



•i of this memoir after the Museum of Comparative Zoology bad 



• ■I for want of funds to postpone its iaaue indefinitely, ha- saved 



the : ii becoming antiquated before they were made public. 



principal studies outside of this Museum wen- made in the Museum 



rdt, and there I received unwearied attention and help from 



and the perb collections. P Q tinted I 



of 'In ive me the benefit of much valuable information, and threw 



without ind I am indebted for similar t 



• W . P - Karl Zittel of the M 



at Munich, and to P M Zurich. The late M Bnrrande, 



Gaudry and I, lr. Fischer of the Jardin des Plantes, 



