13 THE EVOLUTION THEORY 



That the moulting or ecdysis of insects is often hazardous maj- 

 be observed in our own country, and it is familiar to every one who 

 has reared caterpillars. These, too, often fail to get clear of their 

 'cast ' cuticle, and they perish unless artificial aid is given to them. I 

 have never observed any autotomy in them, but in the Phasmids 

 it seems to be a much-used 'device,' and is therefore of great im- 

 portance in the persistence of the species. 



Limbs which are thus thrown off by autotomy regenerate again 

 from the place at which they broke off, that is from the ' suture.' It 

 had been noticed even by the earlier observers (e.g. Goodsir) that there 

 was a jelly-like mass of cells within the joint, and that the develop- 

 ment of the new limb started from this. It might be supposed that 

 the regeneration-primordium is present in the rest of the leg also, but 

 that is not the case, for the animal responds to the tearing off of one 

 joint or of a smaller number than to the suture, not by regenerating 

 the torn part directly, but by amputating the whole of the leg up to 

 the suture, and then from this the regeneration of the whole leg takes 

 place. In the Phasmids the case is similar, but with the difference 

 that regeneration is possible from three places, from the tarsal joints, 

 from the lower third of the tibia, and finally, from the suture between 

 the femur and the trochanter. There is thus a regeneration-primor- 

 dium (Anlage) at the beginning of the tarsal joints, another in the 

 tibia, and a third in the ' suture,' and the first must be equipped,, 

 as we should express it, with the determinants of the five tarsal joints, 

 the second with those for the lower end of the tibia as well, and the 

 third with all the determinants of the whole leg, from the ' suture ' 

 downwards. 



In any case, regeneration is here associated with definite localized 

 pieces of tissue, and is not a general character of all the cells of the 

 leg, and, as it obviously runs parallel at the same time with another 

 adaptation— that of autotomy— there can be no doubt that it too is 

 dominated by the principle of selection, and that it can not only be 

 increased, but that it can be concentrated at particular places and 

 removed from others. But this is only possible if it be bound up with 

 material particles which may be present in or absent from a tissue, 

 and which are therefore a supplement to the ordinary essential 

 constituents of the living cells, although they do not themselves 

 belong to the essential organization. 



I might cite man}^ more examples of localization of regenerative 

 capacity, but will confine myself to one other, which seems to me 

 particularly instructive, because it was first interpreted as an indica- 

 tion of the existence of an adaptive principle in the organism. 



