66 The Bird 



hints of the way it originated. In the lowest of fish-like 

 creatures the Amphioxus, a tiny animal, an inch or two 

 in length, living in the sand along our shores there is 

 a thread-like cord of a gelatinous substance (not carti- 

 lage, however) extending down the back, known as the 

 notochord. He looks like some kind of worm, but this 

 little gristle is his badge of nobility and lilts him clear 



FIG. 42. Amphioxus, one of the lowest vertebrates, with a mere thread of 

 gristle foreshadowing the back-bone of higher animals. This creature bur- 

 rows in the sand along the Atlantic coast. 



of corals, snails, insects, and worms, into the realm of 

 back-boned animals. This notochord lies underneath a 

 thin white line which is all the spinal chord he has, and, 

 at the front end of this, a tiny dot of pigment stands 

 for brain, eye, and ear. Indeed Amphioxus has neither 

 skull, brain, nor limbs. 



The history of the back-bone, like human history, is 

 not altogether a majestic upward evolution; it has its 

 tragedies and set-backs, its hopes and failures. In the 

 waters along our Northern seashores are creatures, some 

 sponge- or lichen-like, others with strange bulb-like bodies 



