II 



INTRODUCTION. xiii 



As alroiulv iiulicateil, the ranj^o of viiriatioii witliiii this class is cxtroinely 

 liiiiitc'il; ami if our views ivsi>ectiiiji; the taxoiioiiiic vahie of the siili- 

 ilivisioiis are iiiliueiiced hy this condition of things, we are olili,!;etl to deny 

 to tlie nnui[is of living liiids the vigliL which lias generally been conceded 

 of ranking as orders. 



'J'he ureatest distinctions existing among the living niemhers of the class 

 are exliihitetl on tiie one liand liv the Ostriches and Kiwis and the related 

 forms, and on the otlier liy all tiie remaining l)irds. 



These contrasted gron])S have been regarded by I'rofessor Huxley as of 

 rdiiial vabie ; but tiie (bfrerences are so slight, in comparison with tiiose 

 whicii iiave received ordinal distinction in other classes, tjiat liie expe- 

 diency of giving them tliat value is extremely doubtful ; and tliey can 

 lie coniliined into one ordei', which may appropriately l)ear the name of 

 h'lir/iljiii/nrii. 



An objection lias lieeii urged to this depreciation of the vahu; of the sub- 

 divisions of the class, on the ground that the jieculiar adaptation for tliglit, 

 wiiicli is tiie prominent cliaracteristie of birds, is incapable of being e<uniiined 

 witli a wider range of form. This is, at most, an exidanatiou of the cause 

 of tiie sb'giit range of variation, and sliould not therefore afl'ect the I'xposi- 

 tioii of tlie /'"■/ (tliereliy admitted) in a classifii'ation iiased on morpiiologieal 

 ciiaracteristics. J>ut it must also lie Ijorne in mind tiiat iligiit is liy no 

 means incomjiatilile with extrenu; modifications, not only of the organs of 

 tligiit, liut of otlier parts, as is well exemplilied in the case of bats and the 

 extinct ])terodactyls, 



\or is tiie class of liirds as now limited confined to the single ordisr of 

 which only we have living reju'esentatives. In fossil forms we have, if the 

 dillereiicrs assumed Ih; coniirmed, ty]ies of two distinct^ orders, one being 

 represeiiled by the genus .1 rc/niop/i ri/>- und another by the genera /cht/ii/iiriii.-i 

 and A/i>i/iiriiix of Maish. The first has been named fSaiiriirir liy Ibeckid ; 

 tlu' second /i/i//ii/iiriii/hi(/rs by ^larsh. 



CompcUeil thus to (|Uestion the existencci (jf any grou|is <if ordinal value 

 among recent liinls, wi' ]iroceed now to examine the grounds nimn which natu- 

 ral sulidivisioiis slicukl be liasiid. The pronunent features in the classilication 

 of the class until recently have been the divisions into groups distinguished 

 liy their adaptation for ditfcrent modes of life ; that is, whether aerial or for 

 ]iiiigivssiiiii on land, for wading or for swimming; or, again, into Land and 

 \\ atei liirds. Such grou]is hav(! a certain value as simjily artificial combi- 

 nations, but wt! nnist not be considered as thereby committing ourselv< s to 

 such a .system as a natural one. 



The time has ,scai<'ely arrived to justify any system of classification 

 hithcrlo ]iropo,scd, and we can only liave a siu'c foundation after an exhaust- 

 ive study of till' osteology, as well ns tlie neurology aiul splanchnology, of the 

 various members. Kiioiigh, however, has already been done to coinince us 

 that the subdivision of the class into Land and Water Jiirds does not exjiress 



