The source of Dragons

[Findegil]

What we can be sure of, is that Dragons do reproduce. The quote below is from Unfinished Tales; part 3: The Third Age; chapter III: The Quest of Erebor; sub-chapter: Extracts from the earlier version, it can be found also in The Annotated Hobbit; Apendix A: The Quest of Erebor where the earlier version is given in full.
Gandlaf had just communicated the idea of taking a Hobbit in to the compnay of Thórin.

"What!" cried Glóin. "One of those simpletons down in the shire? What use on earth, or under it, could he possibly be? Let him smell as he may, he would never dare to come within smelling distance of the nakedest dragonet new from the shell!"

Since Thórin had just before exclaimed that "Dwarves have had more dealings with Dragons than most, and you [Gandalf] are not instructing the ignorant", we are inclined to take this as a clear evidence that Dragons do reproduce by lying eggs. Thus it is quiet possible to bread them. But from what stoke Morgoth started or if they needed female counterparts is not made clear as fare as I am aware of it.

In this respect I tried to find the source of the idea of the dragons bread from eagles. I am nearly sure that it is somewere in The History of Middle-Earth series. And it must be in one of the earlier volumes. But I could not finde it. Anyway I think that it is fairly outdated and could not be taken seriuos.

Respectfully
Findegil