STATES OF INSECTS. 57 



last mortal one shall take place. Can this law, so con- 

 stantly observed, be the result of a blind power ? Or are 

 we to suppose that the Deity himself is always at work 

 to create the necessary organs in their time and place? 

 Is it not much more consonant to reason and the General 

 analogy of nature, to suppose that these parts and organs 

 exist in embryo in the newly-hatched caterpillar, and 

 grow and are successively developed by the action of the 

 nutritive fluid ? In the pupa of many Diptera the in- 

 closed animal, even under the microscope, appears with- 

 out parts or organs, like a mere pulp ; but Bonnet tells 

 us, that if boiled, all the parts of the pupa appear 3 , which 

 proves the preexistence of these parts even when not to 

 be discerned, and that nothing but the evaporation of 

 the fluids in which they swim is wanted to render them 

 visible. 



Mr. William MacLeay has with great truth observed: 

 " The true criterion of animal as well as vegetable per- 

 fection is the ability to continue the species b ;" and in 

 their progress to this state certain changes take place in 

 the parts and organs of all animals and vegetables : 

 there is, therefore, an analogy in this respect between 

 them ; and this analogy also furnishes another argument 

 against Dr. Herold's hypothesis, as we shall presently 

 see. These changes are of three kinds : In the vege- 

 table kingdom, at least in the phaenogamous classes, there 

 is a succession of developments terminating in the ap- 

 pearance of the generative organs, inclosed in the flower ; 

 in this kind the integuments, or most of them, are usually 

 'persistent. In insects and other annulose and some ver- 

 tebrate animals, there is a succession of spoliations, or 



-' QSuvr. viii. 315. b Hor. EiUum'olog. 446. 



