I go THE HISTOEY OF CREATION. 



considered as the necessary results of Natural Selection. 

 The whole tribe, so rich in forms, begins in the Archilithic 

 period with the class of Crabs breathing by gills, and 

 with the lowest Primceval Crabs, or Archicaridse. The 

 form of these Primaeval Crabs, which were developed out 

 of segmented worms, is still approximately preserved by 

 the remarkable Nauplius, in the common larval stage of 

 so many Crabs. Out of the Nauplius, at a later period, 

 the curious Zoea was developed, which is the common 

 larval form of all the higher or mailed crabs (Malacostraca), 

 and, at the same time, possibly of that Arthopod which at 

 first breathed through tracheae, and became the common 

 ancestor of aU Tracheata. This Devonian ancestor, which 

 must have originated between the end of the Silurian 

 and the beginning of the Coal period, was probably most 

 closely related to the still living Primaeval Flies, or 

 Archiptera. Out of these there developed, as the main 

 tribe of the Tracheata, the class of Flies, from the lowest 

 stage of which the spiders and centipedes separated as 

 two diverging branches. Tliroughout a long period there 

 existed only the four biting orders of Flies — the Primaeval 

 flies, Gauze-wings, Straight-wings, and the Beetles, the first 

 of which is probably the common primaiy form of the 

 three others. It was only at a much later period that 

 the Licking, Pricking, and Sipping flies developed out of 

 the Biting ones, which retained the original form of the 

 three pairs of jaws most distinctly. The following table 

 will show once more how these orders succeeded one 

 another in the history of the earth. 



