STRUCTURE OF PUP^.. 297 



some idle doctor, cooped up in his study, has in- 

 vented, that conduce nothing to the ease and happi- 

 ness of life, and from which he expects no other ad- 

 vantage unless that of reaping so much the greater 

 harvest of empty glory from his arguments ; as they 

 contain less of truth and common sense, on account 

 of the extraordinary strength of genius and appli- 

 cation requisite to give an imposing air to such 

 absurdities." 



It was the decided opinion of Swammerdam that 

 the several transformations of insects, particularly the 

 change from the egg to the caterpillar, and from the 

 pupa to the perfect insect, are chiefly affected by the 

 evaporation of the superabundant fluids. Thus he 

 tells us that the nit, or egg of the louse (Pediculus 

 humanusj, is nothing more than the insect itself, 

 which only requires the evaporation of the surround- 

 ing moisture, and the casting of the old skin, to bring 

 it to its perfect form.* It is not a little surprising 

 that so very accurate a naturalist should never have 

 thought of investigating the truth of such an opinion 

 by experiment. That he neglected this precaution is 

 an instance, among thousands more, of the imperfec- 

 tion of human studies ; for his very first trial would 

 have demonstrated the error, which pervades every 

 page of his great work. He was evidently misled 

 into the opinion by perceiving how fluid the contents 

 of an egg or of a pupa are when opened previous to 

 their change, and how dry the insect is upon its 

 evolution. 



It is much more surprising to find Kirby and 

 Spence repeating the same or nearly the same opi- 

 nion, at the very time, too, when they are in the act 

 of quoting the experiments of Reaumur, by which it 

 is refuted, though the great experimenter himself 

 misinterpreted them. " If you open a pupa," say 

 * Sv/ainmerdam, passim. 



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