54 STORY OF THE AMPHIBIANS 



were the beginnings of nerves. Tliej can be recog- 

 nized as having distinct form and structure in those 

 creatures which are well up the scale but yet far below 

 the back-bone. In time the two duties of nerves, that 

 of feeling things and stimulating muscles into action, 

 were separated also, and separate rows of nerve-cells 

 were given to each duty, though the lines lay close 

 alona'side. At the inner end of these two nerve- 

 threads there was a union, which swelled into a little 

 knot called a ganglion. It was simply a little crude 

 brain, which received the news from the outer edge of 

 the creature by one thread, and sent word back by the 

 other, telling the members out there what to do. It 

 was merely the rebounding place where the sensation 

 returned and became stimulation. For a long time 

 these little brains lay disconnected from one another 

 as the early nerve-cells did. They were the lords of 

 their own little realms. Each small margin or fila- 

 ment of the low creatures had its little brain to re- 

 port to and to obey, and literally the right side 

 (there were no hands then) knew not what the left 

 was doing. 



But in time these little brains became connected 

 by nerve-threads, or else they massed themselves into 

 bunches ; and soon these hunches took control of 

 larger areas of tissue ; but we can not attempt to 

 follow this development, which doubtless continued 

 till a great confederacy was formed — which was 

 massed in the back -bone — and then much later a 

 seat of government arose at the forward end of this, 

 which we call the brain. But all of these little brains 



