l8 INHERITANCE IN POULTRY. 



is dominant. But the crest of the first generation hj'brids is always of small 

 size. Likewise, plain head is dominant over cerebral hernia, but some of 

 the hybrids have exceptionall}' high frontal prominences. The white color 

 of crest is recessive in the male hybrids, but is not entirel}' shut out from the 

 females. The high nostril is recessive, yet the presence of its representative 

 in the hybrid gives the latter abnormally wide nostrils. Finally, the comb 

 affords us a case of an organ in which neither parental form can be said to 

 be dominant without such an extension of the term as to render it quite 

 vague. Ever}'' individual shows a modified comb — the Y or shaped comb. 

 This is a new form — a heterozygous form — that probably reappears in the 

 heterozygotes of each generation. 



The facts of correlation show that crest is by no means dependent on 

 cerebral hernia. At the same time I doubt if the absence of present corre- 

 lation disproves the hypothesis that the crest was the result of the hernia. It 

 is at least conceivable that a characteristic that arose as a response to the 

 stimulus of an abnormal ontogenesis should become hereditary and inde- 

 pendent of the stimulus. As for white color on the top of the head, it is 

 dissociable from the crest, for wholly black-crested second hybrids occur. 



Series II.— Single-comb White Leghorn and HouJan. 

 STATEMENT 01' PROBLEM. 



This cross was undertaken for comparison with that between Minorca and 

 Polish, and to test the inheritance of plumage color, extra toe, and face 

 feathering. 



THE RACES AS A WHOLE. 



The Leghorn (fig. 15) is typical of the Mediterranean class of poultrj^ — 

 slender, tall-legged, close- feathered, nervous, and non-broody — the same class 

 as that to which the Minorca belongs. The white Leghorns came originally 

 from northern Italy.* They have been bred in America since 1834. The 

 single-comb variety is one of the most widely bred of our races and has the 

 reputation of being the greatest egg-producer. Considering its white 

 plumage, its transparent skin, with a trace of yellow, and its red iris, it 

 comes very near to being an albino race, but the retina is pigmented. 



The Houdan (fig. 16) comes from France. It, like the Dorking, has 

 doubtless descended from the 5-toed fowls of the Romans, described by 

 Columella, which they probably carried to Gaul in their conquest of that 



* Wright, 1902, p. 385; WyckoflF, 1904, p. 788. 



