on the Direction of Evolution. 177


in this interesting genus, gives us a very important link in the

sequence of phyletic stages.


I venture to predict that the young Tambourine, the

young Cape Dove, and some of their nearer allies, will be found

to have more or less plain traces of the transient marginal

streaks seen in the tertials and long coverts of the Iuca Dove, and

perhaps also dull spots on the outer webs anticipating the spots

of the adult.


Without going into the evidence here, I may say that I

have fully satisfied myself that lateral spots or chequers are

derived from the Turtle-Dove spots, such as are still seen in T.

orientalis, and, in a somewhat reduced form, in the European

Turtle Dove (T. turtur). The mode of derivation was by split-

ting the original central spot in halves. The splitting began at

the apex of the feather, a short-wedge-shaped area of lighter

color (i. e. reduced in pigment) appearing at this point, and ex-

tending more and more inward along the shaft, until the divided

halves became two separate spots or chequers, more or less

pointed at the distal end. The feather thus became double-

spotted. Typical * wedge-shaped areas ' are not rare in domestic

pigeons with the chequered pattern, aud they are very character-

istic marks in the wing of the Guinea Pigeon (C guinea), where

they are described as " triangular white spots." They are seen

again as a specific character in the Spotted Pigeon (C. macidosd)

of South America. They occur also again in the scapulars of

Columba albipennis of Peru and Bolivia.


This simple mode of converting the Turtle-Dove spot into

a pair of lateral chequers is carried out most perfectly in the

posterior scapulars and in the inner secondaries and large

coverts of the wing of the domestic pigeon. As we pass down-

ward towards the lower (outer) edge of the wing, the chequer on

the inner web diminishes in size more or less rapidly, and usually

vanishes before we reach the middle of the wing. The chequer

on the outer web, which lies exposed, diminishes less rapidly,

aud may be continued to or near the outer edge of the wing.


Now chequers are the elements out of which wing-bars

arise. Rows of chequers, as we see them in the young Mourning

Dove, or in the young Passenger Pigeon, or in the chequered—



