AND TIIK PROBLEM OF DIA8TATAXY. 
323 
faulting have become disassociated from the rest of the row, and 
serial with the median coverts from the sixth inwards. Similarly, 
the displaced median coverts 1 — 5 now lie more or less obviously, 
serial with the major coverts, from the sixth inwards. 
By the descent of the feathers 1 — 5 of the second row of minor 
coverts to fill the place of the feathers forming the intercalary row, 
apparent order is restored, the arrangement of the coverts beyond 
being quite orderly, as will be seen by a reference to Fig. 4. 
The wing of the embryo Guillemot is still more instructive, as, 
in this, the shifting does not take place till about hatching time. 
At any rate all, save perhaps the marginal coverts, have made their 
appearance in the shape of papillae before there is any trace of 
shifting, the full extent of which cannot be appreciated till 
a comparison with the wing of the nestling is made, and this is 
completely diastataxic. The study of this wing seems to leave one 
no alternative but that the diastataxic is derived from the eutaxie 
condition. 
So far we have described the covert feathers of the wing as 
running in horizontal series, parallel with the long axis of the wing, 
and for general purposes of convenience in describing external 
characters this may be done. In reality, however, it would seem 
that these coverts really run in transverse series, so that the sum 
of a series of transverse rows makes a horizontal row of major, 
median, or minor coverts, and so on, as the case may be, just as the 
sum of coloured rami of a feather make up the intricate pattern 
which is often present. Thus, in considering the shifting of the 
coverts, we may regard them as moving in horizontal rows or in 
transverse rows, the result will be the same ; but it is important to 
remember the genetic relationship of the feathers in transverse 
rows. 
This remarkable shifting of the transverse rows of coverts 1 — 5 
explains the absence of a remcx from between the fifth pair of 
major coverts, inasmuch as it seems to have thrown the whole 
arrangement between covert and quill out of gear from the fifth 
remex inwards ; resulting, strange though it may appear, in the 
shifting forward, one place of the transverse rows of coverts from 
the sixth row inwards. As a result of this shifting, the sixth major 
covert row becomes attached to the fifth remex, the seventh major 
