EwAET — Variation: Germinal and Environmental. 377 



great-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, not a 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 obtaining 

 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 be a 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 {i.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 probabl}^ 

 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 



TEANS. EOy. DUB. SOC, N.S., VOL. Tir., TART Xlli. 3 G 



