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reason. No doubt it is often expl difficult to distinguish between this power & that of instinct. Thus Dr Hayes in his work on the Open Polar Sea repeatedly remarks that the dogs which were had been drawing the sledges in a body, diverged & separated when they came to thin thin ice, so that their weight might be more evenly distributed. This was often the first notice & warning to which the travellers received that the ice was becoming thin. Now did the dogs act in this manner from the individual experience of each, or from the example of some of the oldest older & more experienced dogs, or from an inherited habit, that is from an instinct?

It is possible that this instinct may might have been acquired since the time, long ago, when dogs were first employed used in drawing their sledges; or the Arctic wolves, the parent-stock of the Esquimaux dog, may have instinctively learnt not to attack when on thin ice their prey in a close pack.

But Such questions are most difficult to answer.)

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Presented to me by Horace Darwin Esq

Feb 14. 1886. The passage is from the MSS of the "Descent of man" & will be found on pg 75 of the Second Edition [illeg] 1882.

Richard Threlfall