213 



When withdrawn they are received into a snug box, where 

 they are so entirely out of the way that they might readily 

 escape notice. 



We now come to the most extraordinarily complex form 

 of the simple hook which it is possible to conceive. It 

 belongs to all caterpillars, with few exceptions. In these the 

 foot consists of a complete circlet of hooks, all having their 

 sharp extremity pointed outwards. The other end is attached 

 to a fibrous band running round the bottom of the leg and 

 connected everywhere by a strong membrane. Fig. 8. Few 

 things can look more formidable than such an apparatus. It 

 is difficult to say what particular purpose this peculiar modi- 

 fication is intended to fulfil. 



There can be no doubt that it is well adapted for locomotion 

 over irregular surfaces. 



Besides the danger which would constantly accrue to the 

 creature itself from these hooks, they would also be greatly 

 in its way when moving along its confined dwelling, were it 

 not for a provision of nature by which these dangers are 

 obviated. 



Two muscles arise from the end of the joint farthest from 

 the foot, and are inserted together into the central membrane 

 connecting the hooks. Fig. 8. 



The integument at the termination of the tarsus is soft, 

 flexible, and elastic to a sufficient distance to enable it to move 

 readily upon itself. 



Whenever the animal wishes to sheath its weapons, the 

 muscles are contracted forcibly to one half of their original 

 length. The hooks are all drawn inwards, each fitting beauti- 

 fully together in their central aspects, and the contraction does 

 not cease until not a vestige of a claw can be seen projecting 

 beyond the leg. Figs. 9 and 10. 



As soon as the necessity has passed away the natural elas- 

 ticity of the skin, kept in abeyance by muscular action for a 

 time, begins to operate and the hooks slowly resume their 



