210 THE WONDER OF LIFE 



of the sow's grunting. Spalding put a young pig into 

 a bag the moment it was born, kept it in the dark for seven 

 hours, and then placed it near the sty, ten feet from where 

 the sow lay concealed. 



' The pig soon recognized the low grunting of its mother, 

 went along outside the sty, strugghng to get under or over 

 the lower bar. At the end of five minutes it succeeded 

 in forcing itself through under the bar at one of the few 

 places where that was possible. No sooner in, than it 

 went without a pause into the pig-house to its mother, 

 and was at once Hke the others in its behaviour '. 



A blind-folded youngster found its mother almost as 

 well as one with its eyes free. After two days blindfolding 

 it required only ten minutes' practice to make it ' scarcely 

 distinguishable from one that had had sight all along '. 



In the strict sense, birds do not learn to fly, though their 

 inborn capacity of flying is improved by exercise. Spalding 

 put five unfledged swallows in a small box with a wire 

 front, and hung it near the nest. The parents fed the 

 offspring through the wires, and the young birds throve as 

 usual, though one was found dead just as it became fully 

 fledged. The others were set free one after another. Two 

 of them were perceptibly wavering and unsteady, and 

 two were more effective from the first. But even the 

 less endowed flew ninety yards right away, and none of 

 them knocked against anything. In a subsequent experi- 

 ment one of the newly-fledged, newly-Uberated birds per- 

 formed almost at once magnificent evolutions over the 

 beech trees. All this was performance without practice, 

 for the swallows had not been able even to extend their 

 wings in their narrow prison. 



In the familiar case of the spider's web, there is no 



