Dennis Ray, age 10, of Canton, N.C.,  for his  question:

How do some animals manage  backbones?

Your backbone is made from a row of small boney rings called vertebrae. They are separated from each other by pads of gristle and stacked like a pile of saucers. Together they make a very strong support for the whole body. Since the whole backbone is made from a number of little bones, it is pliable. You can bend it.

Without this wonderful backbone, you could not stand up or walk around, Besides, it is the center of the skeletons which is the body's supporting framework, And the backbone has another fob, which is dust as important, The vertebrae are hollow rings and piled one upon another they leave a hollow tube down the center of the spine. Through this tube runs the spinal cord. This is a cable of nerve cells which run to and from all parts of the body, The backbone props up the body and it protects the spinal cord, which is a part of the central nervous system.

Animals such as elephants, dogs, kangaroos, birds, frogs, lizards and the true fishes all have backbones very much like yours. They are called the vertebrates   those with vertebrae. But strange to say, most of the animals in the world manage to get along without backbones„ These spineless animals are called the invertebrates,'

A jellyfish has no backbone   no bones of any kind. This is also true of the starfish, the clam and the crab, the snail and the slug. Most of the invertebrates are small creatures, like the busy insects. A few large ones, such as the octopus and the giant squid, are found only in the sea. All these animals get along without a row of vertebrae to prop up the body and without a bonny case to protect the spinal cord.

A big body needs a strong framework, but a small body can get along without one. An insect has no bones. His soft insides are encased and protected in a tough skin.

This system works only  for small animals. That is why no insect ever grows to be as big as,  say, a cat. Invertebrates who live in the sea can overcome this handicap  to some extent. The big octopus uses the water to buoy up his body and give him the support which we get from our bones. vertebrate animals are more highly developed than invertebrates. A bird, for instance, can do a lot more things than a snail can do. To do these extra things, he needs a more complex nervous system. A snail has a very simple nervous system. He can only do a few things and his body does not need many instructions from his nervous system. Most invertebrates have no brains and the central nervous system is a simple cord. They can manage, but they cannot grow very big and they cannot learn to do many different things.