178 THE HISTORY OF CREATION. 



the so-called Zoea, which is of great importance. The order 

 of Schizopoda, those with cloven feet (Mysis, etc.), probably 

 originated from this curious Zoea ; they are at present still 

 directly allied, through the NebaUa to the Phyllopoda, those 

 with foliaceous feet. But of aU living crabs the Phyllopods 

 are the most closely allied to the original primary form of 

 the Nauplius. Out of the Schizopoda the stalk-eyed and 

 sessile-eyed Mailed Crabs, or Malacostraca, developed as 

 two diverging branches in different directions : the former 

 through shrimps (Peneus, etc.), the latter through the Cu- 

 macea (Cuma, etc.), which are still living and closely allied 

 to the Schizopoda. Among those with stalked eyes is the 

 river crab (cray-fish), the lobster, and the others with long- 

 tails, or the Macrura, out of which, in the chalk period, the 

 short-tailed crabs, or Brachyura, developed by the degenera- 

 tion of the tail Those with sessile eyes divide into the 

 two branches of Flea-crabs (Amphipoda) and Louse-crabs 

 (Isopoda); among the latter are our common Rock-slaters 

 and Wood-lice. 



The second main-class of Articulated animals, that of the 

 Tracheata, or air-breathing Tracheate Insects* (Spiders, Cen- 

 tipedes, and Flies) did not develop until the beginning of 

 the palaeolithic era, after the close of the archilithic period, 

 because all these animals (ia contrast with the aquatic crabs) 

 are originally inhabitants of land. It is evident that the 

 Tracheata can have developed only after the lapse of the 

 Silurian period svhen terrestrial life first began. But as fossil 

 remains of spiders and insects have been found, even in the 



* The English word "Insects" might with advantage be used in the 

 Linnsean sense for the whole group of Arthropods. In this case the 

 Hexapod Insects might be spoken of as the Flies. — E. K. L. 



