These two general facts in the economy of organised beings lay a foundation for the existence of diversified races, originating from the same primitive stock and within the limits of identical species." On the following page (page 243) a passage (not marked by Mr.Darwin) emphasises the limitation which Prichard ascribed to the results of variation and inheritance:-- "Even those physiologists who contend for what is termed the indefinite nature of species admit that they have limits at present and under ordinary circumstances.

Whatever diversities take place happen without breaking in upon the characteristic type of the species.

This is transmitted from generation to generation: goats produce goats, and sheep, sheep." The passage on page 242 occurs in the reprint of the 1836-7 edition which forms part of the 1841-51 edition, but is not there marked by Mr.
Darwin.

He notes at the end of Volume I.of the 1836-7 edition: "March, 1857.

I have not looked through all these [i.e.marked passages], but I have gone through the later edition"; and a similar entry is in Volume II.