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174 THE HISTORY OF CREATION. 
tomy, and ontogeny of its four classes, although here, as 
everywhere else, many details remain very obscure. Not 
until the history of the individual development of all the 
different groups has become more accurately known than it 
is at present, can this obscurity be removed. The history 
of the class of Gilled Insects, or Crabs (Carides), is at present 
that best known to us; they are also called encrusted ani- — 
mals (Crustacea), on account of the hard crust or covering of 
their body. The ontogeny of these animals is extremely © 
interesting and, like that of Vertebrate animals, distinctly 
reveals the essential outlines of ths history of their tribe, 
that is, their phylogeny. Fritz Miiller, in his work, “ Fir 
Darwin,” which has already been referred to, has 
explained this remarkable series of facts in a very able 
manner. 
The common primary form of all Crabs, which in most 
cases is even now the first to develop out of the egg, is 
originally one and the same, the so-called Nauplius This 
remarkable primeval crab represents a very simple form of 
articulated animal, the body of which in general has the 
form of a roundish, oval, or pear-shaped dise, and has on its 
ventral side only three pairs of legs. The first of these is 
uncloven, the two subsequent pairs are forked. In front, 
above the mouth, lies a simple, single eye. Although the 
different orders of the Crustacean class differ very widely 
from one another in the structure of their body and its 
appendages, yet the early Nauplius form always remains 
essentially the same. In order to be convinced of this, let 
the reader look attentively at Plates X. and XI., a more de- 
tailed explanation of which is given in the Appendix. On 
Plate XI. we see the fully developed representatives of six 
