174 I'HE 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 the history of their tribe, 

 that is, their phylogeny. Fritz Miiller, in his work, " Fur 

 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 primaeval 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 disc, 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 

 difierent 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 



