240 ME. W. p. PTCHAFT ON SO-CALLED 



5th, thus affoi'ding at the same lime evidence in favour of the 

 view adopted in this paper, that all these coverts have shifted 

 backwards. PI. 15. fig. 1 represents the wing of an embrjo 

 Pigeon showing this intercalary 3rd row very clearly. 



Only one row of ventral coverts appears to participate in the 

 general disturbance which we have traced on the dorsal suifaee 

 in connection with this backward and downward motion of coverts 

 1-5 and remiges 1-4. This is well seen in fig. 3, PI. 14, repre- 

 senting a ventral view of the wing of an embryo Machetes pugnaoc. 



Eefore passing on to consider what is, apparently, the only 

 possible objection to the explanation of the phenomena here set 

 forth, I would draw attention to the accompanying diagrams. 



Pig. 1 a (p. 239) represents the arrangement of the cubital 

 coverts and remiges in the eutaxic wing as far inwards as the 

 9th remex. Pig. 1 h shows the effect of a backward and outw ard 

 shifting of remiges 1-4 and coverts 1-5 from the major coverts 

 forwards ; ^. e., a portion of each horizontal row of coverts from 

 1-5 from the major coverts forw^ards to the tectrices minores, 

 thus converting the eu- into the diasta-taxic wing. The bending 

 of the horizontal lines serves to indicate the amount of shifting 

 which the remiges and coverts have undergone. The arrow " d " 

 has been made to " dip " like the arrows a, b, c, so as to indicate 

 the amount of shifting of each row ; it has also, by means of 

 a dotted line, been made to pass straight outwards to indicate 

 the restoration of parallel series. But it must be remembered 

 that these restored rows are composed of feathers belonging to 

 two different rows. Thus coverts 1-5 of the 2nd row of minor 

 coverts now become serial with the coverts of the 1st row from 

 the 6th inwards, the coverts 1-5 of the 1st row having been 

 cut otf to form a series by themselves — the intercalary row. 

 This intercalary row actually obtains in a more or less well- 

 developed form in all diastataxic wings, and this diagram enables 

 us to see how it may have come into existence. In so far 

 as the diagram is concerned, it is perfectly true that the 1-5 

 coverts of the median row could equally well be regarded as 

 an intercalary row. The size and position of these feathers in 

 the adult probably account for their retention in the series to 

 which they belong. The row (1-5) immediately in front are 

 smaller and more easily isolated; hence these in the adult 

 become the intercalary row. 



The diagram just described (fig. 1, a, I), to show how the eu- 

 may have been transformed into the diasta-taxic wing, can be 



