THE COMING OF A BACKBONE 23 



rudiments of the old skeleton remain as a sort of a quill which 

 has sunk beneath the skin and gives to the body some of 

 the support furnished by our backbone. It was a bold and 

 difficult experiment and was for a time marvellously suc- 

 cessful. The cephalopods were the rulers or vikings of the 

 early palaeozoic seas. No form could begin to compete with 

 them in size and strength. They ruled supreme. 



The vertebrates came upon the scene. Sharks and ganoids 

 were equally swift and had far more efficient jaws. The 

 cephalopods held their place with marvellous pertinacity. 

 Far down in Mesozoic times we find the shells of the ammon- 

 ites very abundant. Possibly the extinction of this great 

 group was due to climatic changes rather than to competition. 

 Certainly the ammonites disappeared. Nautilus is their last 

 surviving near relation. The squids and octopi alone remain 

 of a host of related ancient groups. It is a hopelessly def-eated 

 form, a sad relic of decayed power and greatness. 



Most of our recent squids are of only moderate size. But 

 the body of architeuthis, the giant-squid, is more than eight 

 feet long; while the arms are over thirty feet in length and as 

 thick as a man's thigh; the suckers are as large as coffee-cups. 

 They have been reported from Labrador and Newfoundland, 

 Iceland, Japan, and are apparently deep-water forms of al- 

 most universal distribution. 



A struggle in which squids have been worsted and devoured 

 by fish or even by sperm-whales is a very homely or vulgar 

 sort of tragedy. But let us look a little closer. The ancestor 

 of the squid forsook or refused the crawling life and became 

 free-swimming. This is a step which through the development 

 of muscles, nerves, sense-organs and brain leads to progress. 

 Even sense-organs and brain are stimulated and fostered by 

 muscular locomotion. The goal of early evolutionary progress 

 seems to be first brute strength and toughness, then quick- 

 ness and agility of motion and flexibility of body. We shall 

 see that the vertebrate arose from insignificant beginnings 

 mainly because of its constant exercise of its muscles. The 

 squid played the great game according to its best rules, just 



