178 THE HISTORY OF CREATION, 
the so-called Zoéa, which is of great importance. The order 
of Schizopoda, those with cloven feet (Mysis, etc.), probably 
originated from this curious Zoéa; they are at present still 
directly allied, through the Nebalia to the Phyllopoda, those 
with foliaceous feet. But of all 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, ete.), 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 paleolithic era, after the close of the archilithic period, 
because all these animals (in 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 when 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 
Linnzan sense for the whole group of Arthropods. In this case the 
Hexapod Insects might be spoken of as the Flies.—K. R. L. 
