194 THE HAUNTS OF LIFE 
actual fossils have been found, as they have no 
hard parts which could have been preserved, 
yet we have evidence of the existence of worms 
in the remote past “by the discovery of the 
trails which they have left in crawling over 
soft mud, now hardened into shale or slate, or 
by the burrows which they made in sand, which 
has now been converted into sandstone and 
quartzite... .’ “ Worm-burrows and trails 
are among the oldest fossils yet discovered.” 
FIG. 19.—PERIPATUS. 
A primitive Air-breather, antecedent to Centipedes and the like. 
The second great invasion was that of the 
Air-Breathing Arthropods, led by simple 
jointed-footed animals, well represented by 
a “living fossil,” called Peripatus, an old- 
fashioned creature, surviving from a very 
different world. Peripatus is a beautifully 
coloured soft-bodied animal, worm-like in 
shape, but with simple stumpy limbs, with 
antenne on the head, and two pairs of mouth- 
parts. It lives chiefly in rotting wood, and 
comes out only at night. When it is handled it 
