296 THE MECHANICAL FUNCTIONS* 



moved. But this hypothesis is overturned by 

 the fact that if the animal loses only part of the 

 limb, it is the deficient portion alone, and not the 

 whole limb that is regenerated. The sprouting 

 of the new claw bears a strong analogy to the 

 budding of a plant ; both having their origin 

 from an imperceptible atom, or germ, which is 

 either formed on the occasion, or had pre-existed 

 in the organization. We are, however, totally 

 destitute of the means of deciding which of these 

 alternatives is nearest to the truth. It is but too 

 probable that the agents which can effect such 

 wonderful operations will ever baffle our most 

 scrutinizing inquiries, and that they are of too 

 refined an order to come within the reach of the 

 most subtle conjectures that human imagination 

 can devise. 



Chapter V. 



INSECTS. 



§ 1. Aptera. 



Apterous, or wingless insects form the next term 

 in the series of articulated animals. Closely 

 allied in their organization to many of the pre- 

 ceding families, they differ from them in being 

 essentially formed for a terrestrial instead of an 

 aquatic life. Most of the lower tribes of this 



