The occasional habit of birds laying their eggs in other birds' nests, either of the same or of a distinct species, is not very uncommon with the Gallinaceae; and this perhaps explains the origin of a singular instinct in the allied group of ostriches.
This remarkable instinct was first discovered in the Formica (Polyerges) rufescens by Pierre Huber, a better observer even than his celebrated father.
Smith, I tried to approach the subject in a sceptical frame of mind, as any one may well be excused for doubting the truth of so extraordinary and odious an instinct as that of making slaves.
Such are the facts, though they did not need confirmation by me, in regard to the wonderful instinct of making slaves.
Several cases also, could be given, of occasional and strange habits in certain species, which might, if advantageous to the species, give rise, through natural selection, to quite new instincts.
These domestic instincts, when thus tested by crossing, resemble natural instincts, which in a like manner become curiously blended together, and for a long period exhibit traces of the instincts of either parent: for example, Le Roy describes a dog, whose great-grandfather was a wolf, and this dog showed a trace of its wild parentage only in one way, by not coming in a straight line to his master when called.
Domestic instincts are sometimes spoken of as actions which have become inherited solely from long-continued and compulsory habit, but this, I think, is not true.
Hence, we may conclude, that domestic instincts have been acquired and natural instincts have been lost partly by habit, and partly by man selecting and accumulating during successive generations, peculiar mental habits and actions, which at first appeared from what we must in our ignorance call an accident.
This case is more remarkable than that of the cuckoo; for these bees have not only their instincts but their structure modified in accordance with their parasitic habits; for they do not possess the pollen-collecting apparatus which would be necessary if they had to store food for their own young.
All the above characteristics of instinct can be established by purely external observation, except the fact that instinct does not require prevision.
Moreover, "the well-being of the individual and the preservation of the race" is only a usual characteristic, not a universal one, of the sort of movements that, from our point of view, are to be called instinctive; instances of harmful instincts will be given shortly.
The instincts of an animal are different at different periods of its growth, and this fact may cause changes of behaviour which are not due to learning.
5) That instincts in their nascent stages are easily modifiable, and capable of being attached to various sorts of objects.