MIGRATION 569 
tralians, while among those races who have little or no need to 
exercise it, such as people in the highest state of civilization, and of 
them especially dwellers in towns, the faculty—comparatively weak 
to begin with and undeveloped by practice—perishes through disuse. 
If this variability in possessing the sense of direction? in the human 
species be thus admitted, there can be no impropriety in inferring 
that the lower animals may have the faculty in a degree out of 
all proportion with even those people that have it most. Just as some 
men surpass others in powers of hearing, sight or smell, and many 
animals excel all men in these respects, of all animals the sense of 
direction would naturally attain the greatest perfection in Birds, 
for they are endowed with and exercise the greatest power of loco- 
motion. In urging this opinion there would seem to be no 
theorizing: it is merely arguing from the known to the unknown. 
Nevertheless it is right to take cognizance of all suggestions 
that seem to be reasonable, and among them is one put forth by 
Prof. Mébius (Das Ausland, No. 33, pp. 648, 649, 14 Aug. 
1882) to the effect that Birds performing long migrations over sea 
may be guided by observing the roll of the waves. The possibility 
of this cannot be denied if the roll be constantly in one direction as 
seems likely to be in that part of the Pacific Ocean to which his 
remarks especially refer; but obviously it will not hold good for 
the stormy waters of the North Atlantic, where a swell may be set 
up from any point of the compass, and the American Golden Plovers 
that yearly resort with such punctuality to “the still-vext Ber- 
moothes” would assuredly get but little help on their passage 
thither, or in its continuation to the Antilles, from the set of the 
billows over which they pass—ever varying with the inconstant 
winds. 
Other authors there are who rely on what they call “instinct ” 
as an explanation of this wonderful faculty. This with them is 
simply a way of evading the difficulty before us, if it does not 
indeed remove the question altogether from the domain of scientific 
enquiry. Rejecting such a mode of treatment, Prof. Palmén meets 
it in a fairer spirit. He asserts (Mogl. Flyttn. p. 195), that migrants 
are led by the older and stronger individuals among them, and, 
observing that most of those which stray from their right course 
are yearlings that have never before taken the journey, he ascribes 
the due performance of the flight to “experience.” But, granting 
1 T have no wish to urge this sense of direction as a ‘‘ sixth sense,” as has been 
imputed to me by Dr. Weismann (Nature, xix. pp. 579, 580, 24 April 1879). 
What it may be called does not concern me in the least. I know that it exists, and 
is wholly independent of intellectual forces, as in myself I had proof of the fact 
in my younger days, but want of exercise has impaired its efficacy so as to render 
it almost obsolete. Some would perhaps attribute the effect to ‘‘ unconscious 
cerebration,” and I do not object to the phrase if it seems more explanatory. 
