66 



The Bird 



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

 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 lifts 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 



