Thanks, threeriverschick, for your reply. I appreciate it. Sorry to be so dense, but I understand better when I can see how the theory is applied to specific examples. Stuff that's self-evident to you and others, just isn't always evident to me. Sorry. (Responding to your comment: So you wish me to apply the philosophical statements to these concrete examples? Oh, I thought that was self-evident.) So, I'll have to re-read your reply a few times and stare at it for a while because some of it is a little bit too esoteric for me.
I went and refreshed my memory on who "what'shisname" is. It's Henry B. Wallace of Pioneer, not The Dollar Hen guy. Henry B. Wallace made the Leghorn hybrids by using standard breeding techniques with purebred Leghorns back in the late 1930s - 1940s. Hy-Line. That name, if not the same lines, is still around or was sometime in the last couple of years, for sure. Source of info on Wallace: Margaret Derry's Art and Science of Breeding: Creating Better Chickens, 2012, published Guelph, Ontario. Certainly, some folks, maybe not on this thread, who frequent BYC would own this book. Oddly enough, the book even touches upon the conflict in the 1950s, etc., between traditional breeders and geneticists. I wonder if it's a case of the more things change the more they stay the same.
Are there any breeders of Heritage White Leghorns reading this thread? That would be something, wouldn't it? (APA 1874) To be a Heritage White Leghorn, would the chicken strain have to be free from all influence of the White Leghorns sold by Pioneer and other big breeding companies? Would the strain, then, have to go way back before 1935 to be Heritage? If so, how do you find some strain that has been preserved so long?