{270} <Note in original.> Certainly <two pages in the MS.> ought to be here introduced, viz., difficulty in forming such organ, as eye, by selection. <In the _Origin_, Ed. i., a chapter on _Difficulties on Theory_ follows that on _Laws of Variation_, and precedes that on _Instinct_: this was also the arrangement in the Essay of 1842; whereas in the present Essay _Instinct_ follows _Variation_ and precedes _Difficulties_.> CHAPTER III ON THE VARIATION OF INSTINCTS AND OTHER MENTAL ATTRIBUTES UNDER DOMESTICATION AND IN STATE OF NATURE; ON THE DIFFICULTIES IN THIS SUBJECT; AND ON ANALOGOUS DIFFICULTIES WITH RESPECT TO CORPOREAL STRUCTURES _Variation of mental attributes under domestication._ I have as yet only alluded to the mental qualities which differ greatly in different species. Let me here premise that, as will be seen in the Second Part, there is no evidence and consequently no attempt to show that _all_ existing organisms have descended from any one common parent-stock, but that only those have so descended which, in the language of naturalists, are clearly related to each other. Hence the facts and reasoning advanced in this chapter do not apply to the first origin of the senses{271}, or of the chief mental attributes, such as of memory, attention, reasoning, &c., &c., by which most or all of the great related groups are characterised, any more than they apply to the first origin of life, or growth, or the power of reproduction. The application of such facts as I have collected is merely to the differences of the primary mental qualities and of the instincts in the species{272} of the several great groups. In domestic animals every observer has remarked in how great a degree, in the individuals of the same species, the dispositions, namely courage, pertinacity, suspicion, restlessness, confidence, temper, pugnaciousness, affection, care of their young, sagacity, &c., &c., vary. It would require a most able metaphysician to explain how many primary qualities of the mind must be changed to cause these diversities of complex dispositions. From these dispositions being inherited, of which the testimony is unanimous, families and breeds arise, varying in these respects. I may instance the good and ill temper of different stocks of bees and of horses,--the pugnacity and courage of game fowls,--the pertinacity of certain dogs, as bull-dogs, and the sagacity of others,--for restlessness and suspicion compare a wild rabbit reared with the greatest care from its earliest age with the extreme tameness of the domestic breed of the same animal. The offspring of the domestic dogs which have run wild in Cuba{273}, though caught quite young, are most difficult to tame, probably nearly as much so as the original parent-stock from which the domestic dog descended. The habitual "_periods_" of different families of the same species differ, for instance, in the time of year of