THE WONDER OF LIFE 565 



tarsal joints of the legs of locusts and the like are readily 

 dislocated, and in the two front pairs they are readily 

 regenerated. It requires great force to break the leg near 

 the top between joints 1 and 2 (coxa and trochanter), 

 or still more between parts 2 and 3 (trochanter and 

 femur). The injury is often fatal. But the remark- 

 able point is that if the insect survives and is young, 

 regeneration may be effected, especially if the dislocation 

 is between joints 2 and 3, ivhere it is most difficult. This 

 seems to be an extremely difficult case, for after making 

 all allowances for the various and violent ways in which 

 locusts may be pulled about by one another, or by birds 

 and other enemies, it is difficult to see how in natural con- 

 ditions sufficient force would be exerted to break the 

 leg, and still more difficult to understand why regenera- 

 tion should most frequently follow when the breakage 

 occurs at the most difficult place. 



Yet the difficulty is not insurmountable, for observation 

 of the frequent moultings shows that when the locust is 

 struggling out of its old clothes or cuticle, breakage at 

 the joints is very apt to occur, particularly at the trochanter- 

 femur articulation, which afterwards becomes so strong. 

 The difficulty disappears and becomes an argument in 

 favour of the view that the distribution of the regenerative 

 capacity is adaptive. 



Similarly, Bordage has shown in regard to Walking- 

 Stick Insects, or Phasmids, where the assaults of birds and 

 lizards seemed to afford insufficient reason for the pre- 

 valent habit of breaking off a leg at a particular line and 

 re-growing it thence, that the breakages during emergence 

 from the egg or from the cast moults have probably fur- 

 nished sufficient reason for the evolution of the restorative 



