SI 2 EMBRYOLOGY AND CLASSIFICATION. 



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only the most prominent ones, the correspond- 

 ence between the phases of growth of the young 

 and the relative position of the different groups 

 of adults in their respective classes is very obvi- 

 ous. The worm-like character of the larval con- 

 dition of Insects has been noticed by all ento- 

 mologists, and the crustacean features of their 

 pupa are equally apparent. Neither can the an- 

 alogy be overlooked between the Centipedes and 

 the Worms, or that between the Spiders and Crus- 

 tacea. We have here the fullest evidence that 

 while the highest Insects recall in their earlier 

 condition the permanent character of the adult 

 representatives of the lower classes in their type, 

 those Insects which in their class occupy a middle 

 and lower position, such as the Spiders and Cen- 

 tipedes, also correspond to the lower classes of the 

 same type. Any one familiar with the transfor- 

 mations of Butterflies, and the successive phases 

 of their final development, must have perceived 

 that, even while unfolding its wings, in one sin- 

 gle act preliminary to taking its flight, the But- 

 terfly truly recalls the form and mode of folding 

 the wings peculiar to the Moths and Sphinxes. 

 It is therefore particularly desirable that all 

 these changes should not only be separately de- 

 scribed, as they have been successively observed 

 in different Insects, but minutely compared with 

 on s another, so as to establish with more pre* 



