186 THE HAUNTS OF LIFE 
land reptiles, and birds had their origin in 
land reptiles—where then is the marine an- 
cestrye But the reptiles sprang from an an- 
cient amphibian stock, whose very name, am- 
phibian, suggests that they lived partly in 
water and partly on land. And these am- 
phibians sprang from fishes, and the original 
fishes were in the sea. So that when we say that 
the ancestors of land animals were marine, we 
usually mean their distant ancestors, belonging 
perhaps to a much simpler class. On the other 
hand, when we look at the terrestrial crusta- 
ceans, called wood-lice or slaters, which we see 
running about if we turn over loose stones or 
strip off loose bark, we may safely say these are 
the direct descendants of sea-slaters, such as 
we find to-day among the rocks on the shore. 
TELL-TALE EVIDENCES OF MARINE 
ANCESTRY 
It may be asked, however, why land ani- 
mals may not have begun their existence on 
land, instead of being derived from distant 
ancestors in the sea. This is a good question, 
which requires a longer answer than is pos- 
sible here. But part of the answer is this. 
