Ewart— Variation: Germinal and Environmental. HTL 
ereat-grandparent, one need not hesitate in believing that the resemblance is due 
to the principle of reversion, but when the resemblance is to a supposed ancestor 
thousands of generations removed, one must hesitate before adopting the reversion 
hypothesis. Take, e.g. the following: case :—A cross between a pigeon known to 
fanciers as an ‘‘archangel,” and another known as an ‘‘ owl,” when mated with a 
white fantail, hatched out a bird very like a chequered blue rock pigeon. One 
might say the blue rock-like pigeon was a sport, nota revert. It would, if a sport, 
be a very striking one, and presumably characterized by great prepotency. By 
breeding the blue rock-like cross first with a barb, and then with a white fantail, 
I proved conclusively enough that, instead of being pre-eminently impressive, it 
behaved like any other cross-bred pigeon. Of the two possible explanations, the 
one that regards the blue bird as a revert seems to me to be the simplest, if it 
implies that the restoration of the characters of the blue rock has resulted from 
the ancestral germ-plasm having surged to the surface and obtained control during 
development. One may cross pigeons for many years without, as a fancier would 
say, being lucky enough to produce a blue rock. It can, however, be easily done, 
if certain conditions are observed. The experimenter must first aim at obtaiming 
a nondescript bird—a mongrel in fact—this secured, it should be mated with a 
bird of quite a different strain and history. If the pure bred birds are incapable of 
stamping their characters on the offspring, a bird like a blue rock may be obtained. 
In the ‘‘ owl” we have a not very prepotent bird, probably evolved in North 
Africa; in the ‘‘ archangel” we have a highly specialized but not specially impres- 
sive bird, said to bea product of Northern Russia, and hence not likely to be closely 
related to the owl. It is not surprising that a cross between an owl and an arch- 
angel is absolutely without character, and yet about as far removed from a white 
fantail as could well be imagined. Hence, when crossed with a white fantail the 
germ-plasm in its efforts to form a highly specialized tail, the characteristic snowy 
whiteness, and unique carriage, being unsupported, may completely fail in the 
attempt. On the other hand, the owl-archangel mongrel, being like melted wax, 
counts as nothing, and thus the ancestral germ-plasm (¢.e. the germ-plasm_ repre- 
senting the original stock from which all the numerous varieties of pigeons have 
sprung) asserts itself, and all but entirely controls the development. 
This may not be the true, but it seems to me to be the most feasible, as it is 
the simplest, explanation that can well be offered of what is undoubtedly a very 
remarkable phenomenon—the all but complete restoration of an ancestor probably 
many thousands of generations removed. 
It is worth mentioning that in my restored rock pigeon, the tail, though consist- 
ing of the normal twelve feathers (instead of thirty as in the white fantail sire) is 
slightly expanded at the apex and very slightly arched in the centre; moreover, the 
claw of the left hallux is white, all the others are dark in colour. The single white 
TRANS. ROY. DUB. SOC., N.S., VOL. VII., PART XIII. 3G 
