( in ) 



Table A. 



Mcaftfiremeuts in Millimetres. 



The skeleton of the wing is ver\- 111110,11 reduced in length and in strength. 

 The reduction is most obvious when we compare P. hurrisi with one of the smallest 

 f'ormorants— e.g. mi'lanolewus. In the latter the total length of tlie arm-skeletou 

 is 312 mm., in F.liarrisi it is only 255 mm. Normally the whole wing is more than 

 twice as long as the trunk proper* (cf. Table B), bat in harrisi it is only IDO per 

 cent.— ?'.t'. it is reduced to less than one-half of its normal original size. The degree 

 of reduction is, however, not the same in the various segments (cf Table (!). The 

 humerus is still a strong bone, stouter and thicker than that of a middle-si/.ed 

 Cormorant, and its loss in relative length amounts only to 33 per cent. The fore- 

 arm, ulna and radius, has undergone the greatest reduction, and herewith is 

 correlated the small number of cubital tiuills, while the hand-skeleton is relatively 

 less aflected. 



It is generally stated that reduction of limbs begins at the distal or free end, 

 and I myself have on several occasions endorsed this induction. The present 

 is therefore a good opjwrtunity for correcting this " law," which is certainly not 

 universally ai)plicable to birds. 



Facts : 1. There are well-flying birds with a short humerus (Pigeons), and with 

 a long humerus (Steganopodes, Tiibinares, Storks, etc.). 



2. Increased flying — and above all, sailing power, is concomitant with increased 

 length of the ulna. 



3. In Struthio, Rhea, Alca impennis, Hesperoniis, the humerus is still relatively 

 long, although mostly very slender. The ulna of Rhea is still very long, about 

 three-quarters the length of the humerus, but the hand is much shortened. In 

 Struthio the hand is not so much affected (it carries IG remiges, by far the greatest 



* Tnmk proper, i.e., from the firet ccivico-tlorsal vertebra (lUth of the whole series in I'hnlncro- 

 t'orax) to the last vertebra fused with sacrum and ihum. 



