812 EMBRYOLOGY AND CLASSIFICATION. 
only the most prominent ones, the forrespond- 
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 
one another, so as to establish with more pre- 
