(17/37. 'The Poultry Chronicle' volume 1 page 89.) Mr. Tegetmeier, who has carefully attended to poultry of all breeds, says (17/38. 'The Poultry Book' 1866 page 210.) that Dorking hens, allowed to run with Houdan or Creve-coeur cocks, "produce in the early spring chickens that for size, hardihood, early maturity, and fitness for the market, surpass those of any pure breed that we have ever raised." Mr. Hewitt gives it as a general rule with fowls, that crossing the breed increases their size. He makes this remark after stating that hybrids from the pheasant and fowl are considerably larger than either progenitor: so again, hybrids from the male golden pheasant and female common pheasant "are of far larger size than either parent-bird." (17/39. Ibid 1866 page 167; and 'Poultry Chronicle' volume 3 1855 page 15.) To this subject of the increased size of hybrids I shall presently return.
With PIGEONS, breeders are unanimous, as previously stated, that it is absolutely indispensable, notwithstanding the trouble and expense thus caused, occasionally to cross their much-prized birds with individuals of another strain, but belonging, of course, to the same variety. It deserves notice that, when size is one of the desired characters, as with pouters (17/40. 'A Treatise on Fancy Pigeons' by J.M. Eaton page 56.) the evil effects of close interbreeding are much sooner perceived than when small birds, such as short- faced tumblers, are valued. The extreme delicacy of the high fancy breeds, such as these tumblers and improved English carriers, is remarkable; they are liable to many diseases, and often die in the egg or during the first moult; and their eggs have generally to be hatched under foster-mothers. Although these highly-prized birds have invariably been subjected to much close interbreeding, yet their extreme delicacy of constitution cannot perhaps be thus fully explained. Mr. Yarrell informed me that Sir J. Sebright continued closely interbreeding some owl-pigeons, until from their extreme sterility he as nearly as possible lost the whole family. Mr. Brent (17/41. 'The Pigeon Book' page 46.) tried to raise a breed of trumpeters, by crossing a common pigeon, and recrossing the daughter, granddaughter, great-granddaughter, and great-great-granddaughter, with the same male trumpeter, until he obtained a bird with 15/16 of trumpeter's blood; but then the experiment failed, for "breeding so close stopped reproduction." The experienced Neumeister (17/42. 'Das Ganze der Taubenzucht' 1837 s. 18.) also asserts that the offspring from dovecotes and various other breeds are "generally very fertile and hardy birds:" so again MM. Boitard and Corbie (17/43. 'Les Pigeons' 1824 page 35.), after forty-five years' experience, recommend persons to cross their breeds for amusement; for, if they fail to make interesting birds, they will succeed under an economical point of view, "as it is found that mongrels are more fertile than pigeons of pure race."
I will refer only to one other animal, namely, the Hive-bee, because a distinguished entomologist has advanced this as a case of inevitable close interbreeding. As the hive is tenanted by a single female, it might have been thought that her male and female offspring would always have bred together, more especially as bees of different hives are hostile to each other; a strange worker being almost always attacked when trying to enter another hive. But Mr. Tegetmeier has shown (17/44. 'Proc. Entomolog. Soc.' August 6, 1860 page 126.) that this instinct does not apply to drones, which are permitted to enter any hive; so that there is no a priori improbability of a queen receiving a foreign drone. The fact of the union invariably and necessarily taking place on the wing, during the queen's nuptial flight, seems to be a special provision against continued interbreeding. However this may be, experience has shown, since the introduction of the yellow-banded Ligurian race into Germany and England, that bees freely cross: Mr. Woodbury, who introduced Ligurian bees into Devonshire, found during a single season that three stocks, at distances of from one to two miles from his hives, were crossed by his drones.