212 MR. p. CHALMERS MITCHELL OIN^ SO-CALLED 



fold of the wiag-membrane to the next secondary ; the carpal 

 covert is, like all the secondary major coverts, proximad of the 

 corresponding quill in insertion. After the carpal remex there 

 follow four secoudaries, then a gap which is slightly exaggerated 

 in the drawing, then six other secondaries in even series. The 

 major covert in the gap is bound to the major covert proximal to 

 it by a thin slip of membrane. In Geotrygon montana (PI. 13'. 

 fig. 5) the carpal covert is very small, and under it lies a small 

 remex bound down to the next secondary in normal fashion. 

 Then follow twelve secondaries placed at almost equal distances, 

 so that at first sight the arrangement appears to be eutaxic- 

 Examination of the interspaces, however, shows that there is a 

 small additional covert clearly belonging to the major series but 

 with no corresponding quill. The same condition is very plain' 

 in (Ena capensis; it is only the presence of the covert that makes 

 it possible to regard the wing as diastataxic. The odd covert is 

 plainly crowded, a condition which is still more plain in the 

 specimen than in the diagram, in which for convenience of drawing 

 the relative size of the feathers as compared with the interspaces 

 has been minimized. I have found in a certain number of the 

 Columbse that the wing is practically the same as in Geotrygon 

 and (Ena, with the most important difierence that there appears 

 to be no extra covert, and that, in consequence, the wing must ber 

 regarded as eutaxic, and the group Columbidse added to those 

 among which both eutaxic and diastataxic conditions occur. 

 Nearly tw^o years ago, when I found this eutaxic condition in 

 ColMmiidapicid, I showed the specimens to my friend Mr.Beddard,- 

 in whose laboratory in the Zoological GTardens I was prosecuting 

 my work, and with my consent he noticed the observation in his 

 recent work on Birds (2. p. 305). With that exception the 

 observation is new to literature, and since then I have found 

 the same condition in a number of other pigeons. In Geopelia 

 cuneata (PI. 12. fig. 1) and in G. trangfuilla there are ten pri- 

 maries, each with a distal major covert ; then comes the small 

 carpal covert and remex, the latter with its usual slip binding it 

 to the adjacent secondary ; then follow in even series ten fully- 

 developed secondaries, each with normal proximally-placed major 

 coverts, and in the diastataxic interspace tliere is neither any 

 trace of gap nor an extra covert. In Leucosarcia picata (PL 13. 

 fiff. 2) the conditions are identicalj except that there are eleven 

 fully-developed secondaries. In Geophaps plumifera (Pi. 13. 

 fig. 3) the same condition exists, except that there are twelve 



