vii THE INDUSTRIES OF ANIMALS 133 



is pulled taut. Working from the centre to a foundation - 

 line, always paying out a drag-line and pulling it taut, 

 the spider forms ' ray : ' after " ray," all intersecting at 

 the centre. (3) Having made all the rays, the spinner 

 starts from the centre, and taking big steps moves from 

 ray to ray, leaving a strong spiral thread as it goes. This 

 ' primary spiral ' is not viscid and serves simply as a 

 scaffolding. (4) Finally, working from the outside in- 

 wards, and taking much shorter steps, the spider forms 

 the permanent spiral, which is viscid and adhesive, and 

 forms the chief part of the web. As the secondary spiral 

 is completed, the primary spiral is eaten away. There is 

 often a special thread running from the web to an ad- 



FIG. 39. FLIGHT OF CRESTED HERON, TEN IMAGES PER SECOND. 

 (From Ghambers's Encyclop. ; after Marey.) 



jacent hole where the spider lurks, for it is by vibrations 

 rather than by vision that the advent of visitors is 

 announced. It should be noted that the finer webs are 

 made by the females, which seem to be all equally 

 skilful a feature characteristic of instinctive operations. 

 Another important point is that the first true web a 

 young garden spider makes is on the same general plan 

 as the larger stronger ones afterwards formed. This 

 again is characteristic of instinctive capacity. 



6. Movements. But animals are active in otherTways. 

 All their ways of moving should be considered the mar- 

 vellous flight of birds and insects, the power of swimming 

 and diving, the strange motion of serpents, the leap, the 



