34 THE AGE OF THE EARTH 



to palaeontology as a guide in unravelling the tangled 



history of animal evolution. Peripatus is alive to-day, 



and can be studied in all the details of its structure 



and development ; it is infinitely more ancestral, and 



tells of a far more remote past than any fossil Arthropod, 



although such fossils are well known in all the older 



of the Palaeozoic rocks. And yet Peripatus is not 



known as a fossil. Peripatus has come down, with 



but little chancre, from a time, on a moderate estimate, 



at least twice as remote, and probably many times as 



remote, as the earliest known Cambrian fossil. The 



agencies which, it is believed, have crushed and heated 



the Archaean rocks so as to obliterate the traces of 



life which they contained were powerless to efface this 



ancient type, for, although the passing generations may 



have escaped record, the likeness of each was stamped 



on that which succeeded it, and has continued down 



to the present day. It is, of course, a perfectly trite 



and obvious conclusion but not the less one to be 



wondered at, that the force of heredity should thus far 



outlast the ebb and flow of terrestrial change throughout 



the vast period over which the geologist is our guide. 



If, however, the older Palaeozoic rocks tell us nothing 

 of the origin of the antenna-bearing Arthropods, what do 

 they tell us of the history of the Myriapod and Hexapod 

 Classes ? 



The Myriapods are well represented in Palaeozoic 

 strata, two species being found in the Devonian and no 

 less than thirty-two in the Carboniferous. Although 

 placed in an Order (Archipolypoda) separate from those 

 of living Myriapods, these species are by no means 

 primitive, and do not supply any information as to the 

 steps by which the Class arose. The imperfection of 

 the record is well seen in the traces of this Class ; for 

 between the Carboniferous rocks and the Oligocene 

 there are no remains of undoubted Myriapods. 



We now come to the consideration of insects, of which 

 an adequate discussion would occupy a great deal too 

 much of your time. An immense number of species 

 are found in the Palaeozoic rocks, and these are con- 





