78 THE PHYSICAL KINSHIP 



that the magnificent thinking apparatus of modern 

 philosophers was originally a small sensitive plate 

 developed down in the sea a hundred million years 

 ago on the dorsal wall of the mouths of primeval 

 worms. 



From the worms developed all of the highest 

 four phyla of the animal kingdom — the echino- 

 derms, the mollusks, the arthropods, and the 

 chordate animals, the last of which were the 

 progenitors of the illustrious vertebrates. The 

 lowest of the mollusks are the snails, and from 

 these humble tenants of our ponds and shores 

 sprang the headless bivalves and the giant jawed 

 cuttles. The mollusks were for a long time after 

 their development the mailed monarchs of the 

 sea, and shared with the worms the dominion of 

 the primordial waters. But after the development 

 of the more active arthropods, especially the 

 crustaceans, the less agile worms and mollusks 

 rapidly declined. Existing worms and mollusks 

 are remnants of once powerful and populous 

 races. 



From the worms also developed the arthropods, 

 the water-breathing crustaceans and the air- 

 breathing spiders and insects. The crustaceans 

 came early, away back in the gray of the Silurian 

 period, just about the time North America was 

 born. North America lay, a naked, V-shaped 

 infant, in the regions of Labrador and Canada. 

 The crustaceans rapidly superseded the mollusks 

 as rulers of the sea, attaining, in extreme species, 

 a length of four or five feet. The spiders and 



