Caste - Social insects normally have a number of structurally and functionally different forms: honeybees have queens, workers, and drones: ants have various types of worker such as soldiers and foragers: termites have kings as well as queens and working forms. All the various forms are called castes.

Cataholism - Part of metabolism involving the breakdown of material with release of energy.

Caterpillar - Young stage of various insects (especially, Lepidoptera). The soft body carries three pairs of jointed legs on the thorax and a number of stumpy legs behind Caudal, Concerning the tail.

Cell - All living organisms are composed of one or mote. cells tiny compartments normally invisible to the naked eye within which the vital processes of life go on. In protozoans the body consists of only one cell and all the processes have to go on in that one cell. In many celled animals, however, there are several different types of cell each specialised for a different function. Examples are muscle cells, nerve cells, bone cells, blood cells, and many others. Their shapes and the processes that go on within them differ according to function.

The basis of all living cells is protoplasm. It is important to realise that this is not a single substance, it is a very complicated mixture of organic and inorganic substances in which chemical changes are continuously taking place. The chemical composition of protoplasm therefore varies not only between species and between cells performing different functions but also in individual cells at different times. The main component is water in which there are suspended or dissolved numerous proteins, lipids (fatty substances) and inorganic salts. The electron microscope shows that there is an elaborate structure of fibres and channels within the protoplasm.

Every cell is bounded by a cellmembrane. This is not an external structure but a living part of the cell. The membrane can be seen with the aid of the electron microscope and much other evidence points to its importance. Cells placed in liquid surroundings do not mix with the liquid unless they are pierced with a very fine needle. This suggests some sort of envelope for the protoplasm. Research indicates that the surface layer of the protoplasm consists of a network of protein and lipid material which prevents loss of the cell contents and also allows some flexibility. The thickness of this cell membrane layer is less man one thousand of a millimeter.

Apart from the protoplasm almost all living cells have one structure in common the nucleus. This structure controls the activity of the whole cell and as a rule there is only one nucleus in each cell. It consists largely of nucleoproteins. These regulate the manufacture of the proteins of the rest of the cell protoplasm (cytoplasm). Surrounding the nucleus is a membrane similar to that around the whole cell. There is a darker region within the nucleus called the nucleolus. The nucleus also contains the chromosomes thread like structures that play an important part in cell division and heredity.

It must not be thought that cells consist merely of a nucleus suspended in a bag of protoplasm. There are many other structures to be found in a cell, depending on its function. Most cells are permeated by a system of canals (the endoplasmic reticulum) which probably serves to carry materials to various parts of the cell. The Golgi apparatus is a collection of fatty and protein material which forms tubular bodies, normally in the region of the nucleus. It is found in almost all animal cells but its function is not understood. The centrosome is a region of clear protoplasm near the nucleus. In its centre is a dark body the centriole which seems to be connected with cell division. Throughout the cell division. Throughout the cell protoplasm there are numerous tiny bodies called mitochondria. They are concerned with the respiratory mechanisms of the cell and are most numerous when the cell is most active. Gland cells and some others contain secretory granules which produce hormones or enzymes that are passed out to other parts of the body. Every cell in the body originates from another by division for every creature starts life originally as a single cell.

Central Nervious System - (C.N.S.). The brain and spinal cord or main nerve cord of the body. The central nervous system co ordinates the activity of the whole body because all stimuli are transmitted to it and the appropriate responses originate from it.

Centrum - The central part or body of a vertebra. It replaces the notochord during development in most verebrates.

Cephalochordata - (=Acrania) a subphylum of the Chordata containing Amphioxus and a few related animals. These animals have a dorsal, hollow nerve cord, a notochord, and gill slits all typical features of chordates. Although they have no branin as such and no skull or skeleton, these creatures probably represent the early ancestors of the fishes. Amphioxus lives around the coasts of all the seas where it burrows in the sand. It draws a current of water in through its mouth and passes it to the pharynx which has numerous gill slits. The gill bars hold back any small particles of food and let the water pass out into the atrium. From there it passes through a small pore and out to the sea again. The trapped food particles, mixed with slime are swept by ciliary action into the mid gut for digestion.

Cephalopoda - A class of the phylum Mollusca containing the squids, octopuses, and cuttlefish, all of which are marine. There are many extinct members ammonites, belemnites, and others typically with a chambered sell. Modern forms, however, except for the Pearly. Nautilus have a very reduced shell. In size they very from a few inches to 60 feet the length of a giant squid including tentacles.

At first inspection the relationship between these animals and the slugs, snails and mussels is not very obvious. But it is made clearer by considering a cephalopod in an upside down position.

As in all molluscs a thick layer of skin (the mantle) surrounds the internal organs. The shell is usually secreted inside the mantle. In octopuses it is represented by a pair of small rods or a thin plate. In octopuses it is better developed, and forms a calcareous, shield shaped object familiar as the canary's cuttlebone or sea biscuit. Squid shells (called pens) are slender and are made of chitin.

Cephalopods differ from other molluscs in having a distinct head, marked off from the rest of the body by a narrower 'neck'. The mantle does not cover the head; it slaps at the neck and there forms a loose fold called the collar. The mantle is muscular and alternately expands and contracts. When it expands water is drawn in around the collar. The water fills a space between the inside structures of the creature and the mantle. This space is the mantle cavity and projecting into it are two delicate filaments of tissue the gills. The gills absorb oxygen from the water.

The water does not pass out the same way as it came in. When the mantle cavity is full, the entrances at the collar are closed ,and the cavity becomes a compression chamber. As the muscular mantle contracts, the water is forced out through a single narrow outlet, the siphon, situated on the underside of the head. When necessary the water may be pumped out with great force which gives the creature jet propulsion in the opposite direction to which the siphon is pointing.

The most conspicuous structures of all cephalope as are the arms surrounding the head. The anus (together with the siphon) really correspond to the foot of the snail and mussel. The name cephalopod means in fact headfooted (Greek, kephale, a head; podos, a foot). The octopuses have eight arms while the squids and cuttlefish have ten, two of them longer than the rest and called tentacles.

The arms are equipped with numerous suckers. There may be a single or a double row according to the species. Each sucker is a remarkable structure. In the octopus it consists of a flat muscular disc supported on a consists of a flat muscular disc supported on a cushion of tissue. When the octopus grabs hold of an object, the outer thickened rim of the sucker firmly presses against the surface, giving it a water tight contact. Then the centre of the disc is raised like a piston by muscular contraction. A partial vacuum is created inside the sucker and gives the octopus a strong grip. The suckers are very sensitive to mechanical and chemical sensation, and are also used as. organs for exploration. The suckers of squids and cuttlefish are toothed.

The mouth is armed with a horny beak made of chitin. The beak consists of two hard, pointed plates which work against one another. Inside the mouth is a tongue strengthened with cartilage and covered by the radula-a strip of tissue covered with rows of curved rasping teeth.

Compared with other molluscs cephalopods lead a very active life and have a correspondingly better developed nervous system with a large brain. The animals feed on crabs, prawns, fish, and other molluscs. They find their food by sight and their eyes are very good, in fact they show remarkable similarities to vertebrate eyes.