1424 THE STORY OF THE UNIVERSE 



It appears, then, that there are good grounds for 

 considering that the various types of insects are de- 

 scended from ancestors more or less resembling the 

 genus Campodea, with a body divided into head, 

 thorax, and abdomen ; the head provided with mouth- 

 parts, eyes, and one pair of antennae; the thorax with 

 three pairs of legs; and the abdomen, in all proba- 

 bility, with caudal appendages. 



If these views are correct, the genus Campodea 

 must be regarded as a form of remarkable interest, 

 since it is the living representative of a primeval type, 

 from which not only the Collembola and Thysanura, 

 but the other great orders of insects have derived 

 their origin. 



Since, then, individual insects are certainly in many 

 cases developed from larvae closely resembling the 

 genus Campodea, why should it be regarded as in- 

 credible that insects as a group have gone through 

 similar stages? That the ancestors of beetles under 

 the influence of varying external conditions, and in 

 the lapse of geological ages, should have undergone 

 changes which the individual beetle passes through 

 under our own eyes and in the space of a few days, is 

 surely no wild or extravagant hypothesis. Again, 

 other insects come from vermiform larvae much re- 

 sembling the genus Lindia, and it has been also re- 

 peatedly shown that in many particulars the embryo 

 of the more specialized forms resembles the full- 

 grown representatives of lower types. I conclude, 

 therefore, that the Insecta generally are descended 

 from ancestors resembling the existing genus Cam- 

 podea, and that these again have arisen from others 



