74, MEANING OF ORDERS. 
cea, the front one being the largest; and in the 
Insects there are three nervous centres, the larg- 
est in the head, a smaller one in the chest, and 
the smallest in the hind body. Now according 
to this greater or less individualization of parts, 
with the corresponding localization of the ner- 
vous centres, naturalists have established the rel- 
ative rank of these three groups, placing Centi- 
pedes lowest, Spiders next, and Winged Insects 
highest. But naturalists may, and indeed ‘they 
actually do, differ as to this estimation of the 
anatomical structure, for the Spiders are placed 
above Insects by some naturalists, and many even 
eonsider them a distinct class. Have we, then, 
any means of testing its truth to Nature? Let us 
look at the development of these animals, taking 
the highest order as an illustration, that we may 
have the whole succession of changes. 
All know the story of the Butterfly with its 
three lives, as Caterpillar, Chrysalis, and Winged 
Insect. I speak of its three lives, but we must 
not forget that they make after all but one life, 
and that the Caterpillar is as truly the same be- 
ing with the future Butterfly, as the child is the 
same being with the future man. The old signifi- 
cance of the word metamorphosis — the . fabled 
transformation of one individual into another, in 
which so much of the imagination and poetical 
culture of the ancients found expression — still 
