TRANSACTIONS OF SECTION D. 793 



how vastly the sense of direction varies in human beings, contrasting its absence 

 in the dwellers in towns compared with the power of the shepherd and the 

 countryman, and, infinitely more, with the power of the savage or the Arab, fie 

 adduces the experience of Middendorff among the Samojeds, who know how to 

 reach their goal by the shortest way through places wholly strange to them. He 

 had known it among dogs and horses (as we may constantly perceive), but was 

 surprised to find the same incomprehensible animal faculty unweakened among 

 uncivilised men. Nor could the Samojeds understand his inquiry how they did 

 it. They disarmed him by the question, How now does the arctic fox find its way 

 aright on the Tundra, and never go astray ? and Middendorff adds : ' I was thrown 

 back on the unconscious performance of an inherited animal faculty;' and so are we ! 



There is one more kind of migration, on which we know nothing, and where 

 the field naturalist has still abundant scope for the exercise of observation. I 

 mean what is called exceptional migration, not the mere wanderings of waifs 

 and strays, nor yet the uncertain travels of some species, as the crossbill in search 

 of food, but the colonising parties of many gregarious species, which generally, 

 so far as we know in our own hemisphere, travel from east to west, or from 

 south-east to north-west. Such are the waxwing (A^npelis garrula), the pastor 

 starling {Pastor roseus) and Pallas's sandgrouse, after intervals sometimes of 

 many years, or sometimes for two or three years in succession. The waxwing 

 will overspread Western Europe in winter for a short time. It appears to be 

 equally inconstant in its choice of summer quarters, as was shown by J. Wolley in 

 Lapland. The rose pastor regularly winters in India, but never remains to breed. 

 For this purpose the whole race seems to collect and travel north-west, but 

 rarely, or after intervals of many years, returns to the same quarters. Verona, 

 Broussa, Smyrna, Odessa, the Dobrudscha, have all during the last half-century been 

 visited for one summer by tens of thousands, who are attracted by the visitations 

 of locusts, on which they feed, rear their young, and go. These irruptions, how- 

 ever, cannot be classed under the laws of ordinary migration. Not less inexpli- 

 cable are such migrations as those of the African darter, which, though never yet 

 observed to the north of the African lakes, contrives to pass, every spring, unob- 

 served to the lake of Antioch in North Syria, where I found a large colony rearing 

 their young ; and which, so soon as their progeny was able to fly, disappeared to 

 the south-east as suddenly as they had arrived. 



There is one possible explanation of the sense of direction unconsciously exer- 

 cised, which I submit as a working hypothesis. We are all aware of the instinct, 

 stroug both in mammals and birds without exception, which attracts them to the 

 place of their nativity. When the increasing cold of the northern regions, in 

 which they all had their origin, drove the mammals southward, they could not 

 retrace their steps, because the increasing polar sea, as the arctic continent sank, 

 barred their way. The birds reluctantly left their homes as winter came on, and 

 followed the supply of food. But as the season in their new residence became 

 hotter in summer, they instinctively returned to their birthplaces, and there 

 reared their young, retiring with them when the recurring winter impelled 

 them to seek a warmer climate. Those species which, unfitted for a greater 

 amount of heat by their more protracted sojourn in the northern regions, per- 

 sisted in revisiting their ancestral homes, or getting as near to them as they 

 could, retained a capacity for enjoying a temperate climate, which, very gra- 

 dually, was lost by the species which settled down more permanently in their 

 new quarters, and thus a law of migration became established on the one side, and 

 sedentary habits on the other. 



If there be one question on which the field naturalist may contribute, as lion's 

 provider to the philosopher, more than another, it is on the now much disputed 

 topic of ' mimicry,' whether protective or aggressive. As Mr. Beddard has re- 

 marked on this subject, ' The field of hypothesis has no limits, and what we need 

 is more study' — and may we not add, more accurate observation of facts P The 

 theory of protective mimicry was first propounded by Mr. H. W, Bates, from his 

 observations on the Amazon. He found that the group of butterflies, Heliconiidce, 

 conspicuously banded with yellow and black, were provided with certain glands 



