CRUSTACEA. 265 



embryo limbs, ready to be developed as occasion 

 might require ; somewhat in the way in which the 

 rudiments of the secondary teeth remain concealed 

 in the jaw, in preparation for replacing the first set 

 when these had been removed. But this hypo- 

 thesis is overturned by the fact that if the animal 

 loses only part of the limb, it is the deficient por- 

 tion alone, and not the whole limb which is rege- 

 nerated. 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, how- 

 ever, 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 imagi- 

 nation 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 preceding 

 families, they differ from them in being essentially 



* The Linnean order of Aptera has, more recently, been broken 

 up and distributed among other orders of insects, according to their 



