Dissection and microscope show that hybrid is in exactly same condition as another animal in the intervals of breeding season, or those animals which taken wild and _not bred_ in domesticity, remain without breeding their whole lives. It should be observed that so far from domesticity being unfavourable in itself <it> makes more fertile: [when animal is domesticated and breeds, productive power increased from more food and selection of fertile races]. As far as animals go might be thought <an> effect on their mind and a special case. {65} The meaning is "That sterility is not universal is admitted by all." {66} See _Var. under Dom._, Ed. 2, i. p. 388, where the garden forms of _Gladiolus_ and _Calceolaria_ are said to be derived from crosses between distinct species. Herbert's hybrid _Crinums_ are discussed in the _Origin_, Ed. i. p. 250, vi. p. 370. It is well known that the author believed in a multiple origin of domestic dogs. {67} The argument from gradation in sterility is given in the _Origin_, Ed. i. pp. 248, 255, vi. pp. 368, 375. In the _Origin_, I have not come across the cases mentioned, viz. crocus, heath, or grouse and fowl or peacock. For sterility between closely allied species, see _Origin_, Ed. i. p. 257, vi. p. 377. In the present essay the author does not distinguish between fertility between species and the fertility of the hybrid offspring, a point on which he insists in the _Origin_, Ed. i. p. 245, vi. p. 365. {68} Ackermann (_Ber. d. Vereins f. Naturkunde zu Kassel_, 1898, p. 23) quotes from Gloger that a cross has been effected between a domestic hen and a _Tetrao tetrix_; the offspring died when three days old. {69} No doubt the sexual cells are meant. I do not know on what evidence it is stated that the mule has bred. {70} The sentence is all but illegible. I think that the author refers to forms usually ranked as varieties having been marked as species when it was found that they were sterile together. See the case of the red and blue _Anagallis_ given from Gaertner in the _Origin_, Ed. i. p. 247, vi. p. 368. {71} In the _Origin_, Ed. i. p. 258, where the author speaks of constitutional differences in this connexion, he specifies that they are confined to the reproductive system. {72} The sensitiveness of the reproductive system to changed conditions is insisted on in the _Origin_, Ed. i. p. 8, vi. p. 10. The ferret is mentioned, as being prolific in captivity, in _Var. under Dom._, Ed. 2, ii. p. 90.