I90 THE HISTORY 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 Primeval Crabs, or Archicaride. The 
form of these Primzval Crabs, which were developed out 
of segmented worms, is still approximately preserved by 
the remarkable Nawplius, in the common larval stage of 
somany Crabs. Out of the Nauplius, at a later period, 
the curious Zoéa 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 trachez, and became the common 
ancestor of all 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 Primeval 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. Throughout along period there 
existed only the four biting orders of Flies—the Primeval 
flies, Gauze-wings, Straight-wings, and the Beetles, the first 
of which is probably the common primary 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. 
