1884.] on the Darwinian Theory of Instinct. 137 



In order to demonstrate this principle of the variation of instinct 

 under the guidance of intelligence, I may here introduce a few 



Huber observes, " How ductile is the instinct of bees, and how 

 readily it adapts itself to the place, the circumstances, and the needs 

 of the community." Thus, by means of contrivances which I need 

 not here explain, he forced the bees either to cease building combs, or 

 to change their instinctive mode of building from above downwards, 

 to building in the reverse direction, and also horizontally. The bees 

 in each case changed their mode of building accordingly. Again, an 

 irregular piece of comb, when placed by Huber on a smooth table, 

 tottered so much that the bumble bees could not work on so unsteady 

 a basis. To prevent the tottering, two or three bees held the comb 

 by fixing their front feet on the table, and their hind feet on the comb. 

 This they continued to do, relieving guard, for three days, until they 

 had built supporting pillars of wax. Some other bumble bees, when 

 shut up and so prevented from getting moss wherewith to cover 

 their nests, tore threads from a piece of cloth, and " carded them with 

 their feet into a fretted mass," which they used as moss. Lastly, 

 Andrew Knight observed that his bees availed themselves of a kind 

 of cement made of rosin and turpentine, with which he had covered 

 some decorticated trees — using this ready-made material instead of 

 their own propolis, the manufacture of which they discontinued ; and 

 more recently it has been observed that bees, " instead of searching 

 for pollen, will gladly avail themselves of a very different substance, 

 namely, oatmeal." Now in all these cases it is evident that if, from 

 any change of environment, such accidental conditions were to occur 

 in a state of nature, the bees would be ready at any time to meet 

 them by intelligent adjustment, which, if continued sufficiently long 

 and aided by selection, would pass into true instincts of building 

 combs in new directions, of supporting combs during their construc- 

 tion, of carding threads of cloth, of substituting cement for propolis 

 and oatmeal for pollen. 



Tui'ning to higher animals, Andrew Knight tells us of a bird 

 which, having built her nest upon a forcing-house, ceased to visit it 

 during the day when the heat of the house was sufficient to incubate 

 the eggs ; but always returned to sit upon the eggs at night when the 

 temperature of the house fell. Again, thread and worsted are now 

 habitually used by sundry species of birds in building their nests, 

 instead of wool and horse-hair, which in turn were no doubt originally 

 substitutes for vegetable fibres and grasses. This is especially 

 noticeable in the case of the tailor-bird, which finds thread the best 

 material wherewith to sew. The common house-sparrow furnishes 

 another instance of intelligent adaptation of nest-building to circum- 

 stances, for in trees it builds a domed nest (presumably, therefore, the 

 ancestral type), but in towns avails itself by preference of sheltered 

 holes in buildings, where it can afford to save time and trouble by 

 constructing a loosely-formed nest. Moreover, the chimney- and 

 house-swallows have similarly changed their instincts of nidification. 



