Phylclic Parallelism in Metamorphic Species. 497 



change. It. is to me incomprehensible how one 

 and the same vital force can in the same indi- 

 vidual induce one stage to become transformed 

 feebly and the other stage strongly, these trans- 

 formations corresponding in extent with the 

 stronger or weaker deviations in the conditions of 

 life to which the organism is exposed in the two 

 stages ; to say nothing of the fact that by such 

 unequal divergences the idea of a perfect system 

 (creative thought) is completely upset. 



Nor can the objection be raised that we are 

 here only concerned with insignificant changes 

 with nothing more than the arrested development 

 of single organs and so forth, in brief, only with 

 those changes which can be ascribed to the action 

 of the environment. 



We are here as little concerned with a mere 

 suppression of organs through arrested develop- 

 ment as in the case of the Cirripedia ; the trans- 

 formation and reconstruction of the whole body 

 goes even much further than in these Crustacea, 

 although not so conspicuous externally. Where 

 do we elsewhere find insects having the head 

 inside a cavity of the body (sectorial head of the 

 Muscida), and of which the foremost segment 

 the physiological representative of the head 

 consists entirely of the coalesced antennae and 

 pairs of maxillae ? 



The incongruences in the form-relationships 

 are, however, exceedingly numerous in the case 



K k 



