324 
MR. W. P. PYCRAFT ON THE BIRDS WING 
covert to the sixth remex, and so on to the innermost remex. Thus, 
the major coverts 1 — 4 become attached to the remiges which, in 
the embryonic wing, lie immediately behind them, and the major 
coverts from number six inwards are attached to the remiges 
immediately in front of them, leaving the fifth covert completely 
divorced from its original moorings. See Fig. 5. 
Diastataxy is not a sporadic feature or confined to a few species, 
on the contrary, it is characteristic of many large groups of birds. 
For instance the Megapodes, Geese ; Steganopodes — e.g., Gannets, 
Cormorants, Frigate-birds; Storks, Herons ; New World Vultures, 
Hawks, Eagles, and Old World Vultures; Cranes; Limicoke — e.g., 
Sand-pipers, Snipe, Curlews, Plovers ; Pigeons ; Petrels ; Divers 
and Grebes ; are all diastataxical. So also are the Parrots, Owls, 
Night-jars, and many Kingfishers and Swifts. 
But there are some puzzling exceptions to this rule which were 
very baffling until it was shown by Dr. P. Chalmers Mitchell, that 
at least in many cases the supposed eutaxial discordant forms were 
really diastataxial. The groups of birds in which this pseudo-eutaxy 
has been proved are the Pigeons and Kingfishers. What obtains 
here probably explains the exceptions met with also among the 
Swifts, and certain aberrant members of the Gruidae. 
In studying these exceptions we must first of all notice that the 
process of shifting, which we have already described, brought 
about a distinct gap between the fourth and fifth remiges, a gap 
which, regarded in conjunction with the fact that the fifth pair of 
major coverts in such cases embraced no remex, lent colour to the 
view — that a remex was actually missing. 
Within the limit of this gap, when normally developed, will be 
found a major, and on either side of it a median covert. In the 
apparently eutaxial Pigeons the gap has become reduced so as not 
to exceed the space dividing the remainder of the secondary 
remiges one from another. The two median coverts become 
markedly reduced, and finally, in some Pigeons, disappear 
altogether, whilst the major covert becomes so reduced as to give 
it a superficial appearance to one of the two missing median 
coverts. The wing thus appears to be eutaxial. Since, however, 
the dorsal and ventral major coverts still remain, the wing is, 
undoubtedly, diastataxic. 
