( 402 ) 



Apteri/x hnnati, althongh looking like a larger edition of A. oweni, differs in the 

 last two features just mentioned. 



Apteri/x mantelli and A. australis are closely allied to each other, and come 

 very much nearer to A. haasti than to A. oweni. The following tabular statement 

 deals with many of the points raised in the present paper. 



It will he observed that a very large proportion of the structural variations, 

 observed by myself and others among the species of Apteryx, concern degenerating, 

 or at least altering, organs ; they are mainly indeed massed in the wing and adjacent 

 parts, which is of course precisely where degeneration is most actively progressing. 

 These very numerous variations cannot, therefore, be safely regarded as a basis 

 of classification. In different individuals the processes may be easily supposed to be 

 going on with more accelerated or with less rapidity than in others. The wing of 

 Apteri/x seems to be too small to be useful in any way, and yet too large to enable 

 us to assume that a position of equilibrium has been reached. The specific characters, 

 therefore, in that region of the body are not yet fi.xed ; we can at most observe 

 tendencies towards particular structural peculiarities. It would seem, for example, 

 that the sternum of A. haa.iti varies round a long and comparatively narrow form, 

 and that a short comparatively wide sternum is equally distinctive of A. mantelli ; 

 that perhaps A. kaa»ti has definitely acquired a solid coracoid without an anterior 

 notch, while A. mantelli and A. australis have nut settled down to a state of rest in 

 this particular. On the other hand, the syrinx and the hind hmb would seem to 

 offer more reliable material whereon to base specific distinction. 



