It is worthy of remark, that as many organic beings, when taken by man out of their natural conditions, have their reproductive system <so> affected as to be incapable of propagation, so, we saw in the first chapter, that although organic beings when taken by man do propagate freely, their offspring after some generations vary or sport to a degree which can only be explained by their reproductive system being <in> some way affected. Again, when species cross, their offspring are generally sterile; but it was found by Koelreuter that when hybrids are capable of breeding with either parent, or with other species, that their offspring are subject after some generations to excessive variation{258}. Agriculturists, also, affirm that the offspring from mongrels, after the first generation, vary much. Hence we see that both sterility and variation in the succeeding generations are consequent both on the removal of individual species from their natural states and on species crossing. The connection between these facts may be accidental, but they certainly appear to elucidate and support each other,--on the principle of the reproductive system of all organic beings being eminently sensitive to any disturbance, whether from removal or commixture, in their constitutional relations to the conditions to which they are exposed. {258} _Origin_, Ed. i. p. 272, vi. p. 404. _Points of Resemblance between "Races" and "Species{259}."_ {259} This section seems not to correspond closely with any in the _Origin_, Ed. i.; in some points it resembles pp. 15, 16, also the section on analogous variation in distinct species, _Origin_, Ed. i. p. 159, vi. p. 194.