adult life they spend most of their time on the trunks of trees, where they receive immunity from attack because of their color markings. The feet of the tree toad are modified for climbing by having little disks on the ends of the toes, by means of which it is passing through the stages of the segmenting egg, with few exceptions they breathe by means of external gills; later they may develop lungs. A few never have lungs, but breathe through the moist skin. Newt. From photograph loaned by the American Museum of Natural History. Still other amphibians are the mud puppies, sirens or mud eels, and the axolotl. All of the above animals differ from the reptiles in having a smooth skin with no scales, and in passing the early stage of their existence in the water. CLASSIFICATION OF AMPHIBIA MENTIONED ORDER I. Urodela. Amphibia having usually poorly developed appendages. Tail persistent through life. Examples, mud puppy, newt, salamander. ORDER II. Anura. Tailless amphibia, which undergo a metamorphosis breathe by gills in larval, by lungs in adult, state. Examples, toad and frog. REFERENCE BOOKS FOR THE PUPIL Davison, Practical Zoology, pages 199–211. American Book Company. Hunter and Valentine, Laboratory Manual of Biology, pages 170-177. Henry Holt and Company. Jordan, Kellogg, and Heath. Animal Studies. D. Appleton and Company. FOR THE TEACHER Holmes, The Biology of the Frog. The Macmillan Company. Parker and Haswell, Text-book of Zoology. The Macmillan Company. XXIV. REPTILES The Spotted or Mud Turtle (Chelopus guttatus). For a classroom exercise use living turtles. The body is flattened, and is covered on the dorsal and ventral sides by a bony framework. This covering is seen to be made up of a number of scales or plates cemented together to form one bony cover. What is the general arrangement of these plates? The dorsal covering is known as the carapace, the ventral one the plastron, the connection between them the bridge. Allow the animal to remain quiet for a moment, then touch the head suddenly. What is one function of the shell? In the box turtle this adaptation is made more evident by the presence of bony plates which fit over the head and legs after they are withdrawn into the shell. Adaptations. Place a lively turtle on its back. How does it attempt to regain equilibrium? Notice the long neck. The long neck and powerful horny jaws are of great use to the animal in food getting. Allow the turtle to crawl on the table. Then place it in a dish of water. How are the legs adapted to movement in the water? How is the foot adapted for other purposes? Turtles are very strong for their size. The stout legs carry the animal slowly on land, and in the water, being slightly webbed, they are of service in swimming. The strong claws are used for digging especially at egg-laying season, for some forms of turtles dig large holes in sandy beaches in which the eggs are deposited. Watch a turtle feeding. Notice that the claws are used. How? The absence of teeth makes it necessary for the turtle to tear the food with the aid of the strong claws. Painted turtle. The sense of hearing in the turtles is not keen. The tympanic membrane can be seen just behind the eyes on the sides of the head. Can you determine by experiment anything regarding keenness of vision in the turtle? Is the turtle protectively colored? Describe any evidences you may see. Notice that the yellow, ventral side would harmonize the general coloring, looking through the water toward the surface of the pond. The yellow dots on the black background look in the water much like small stones or sand grains. Draw the turtle, natural size, from the dorsal side and label all the parts you know. The Turtles. The turtles form a large and interesting group of animals. They are mostly aquatic in habit. Some exceptions are found, however, as in the case of the box tortoise (Cistudo Carolina) and the giant tortoise of the Galapagos Islands. This latter animal attains a weight of three hundred pounds or more and may be over four feet in length and almost three feet in thickness. Many of the sea-water turtles are of large size, the leatherback and the green turtle often weighing six hundred to seven hundred pounds each. The flesh of the green turtle and especially the diamond back terrapin, an animal found in the salt marshes along our southeastern coast, are highly esteemed as food. Unfortunately for the preservation of the species, these animals are usually taken during the breeding season, when they go to sandy beaches to lay their eggs. Box tortoise (Cistudo Carolina). From photograph loaned by the American Museum of Natural History. Characteristics of the Reptilia. - The turtle belongs to the class of vertebrates known as the Reptilia. These animals are characterized by having scales developed from the skin. These in the turtle have become bony and are connected with the internal skeleton. Turtles always breathe by means of lungs, differing in this respect from the amphibians. They show their distant relationship to birds in that their eggs are large and are encased in a leathery, limy shell. Lizards. Lizards may be recognized by the long body with four legs of nearly equal size. The body is covered with scales. The animal never lives in water, it is active in habit, and it does not undergo a metamorphosis. Salamanders (commonly called lizards) have a moist skin, and belong to the Amphibia. Lizards are harmless creatures, the Gila monster of New Mexico and Arizona, a poisonous variety, being the one exception. Lizards are, on the whole, of economic importance to man because they eat insects and include the injurious ones in their dietary. Certain lizards, including injurious ones, notably the chameleon and our common fence lizard, have the power to change the color of the skin. This forms a protective adaptation, for they thus assume the color of their immediate surroundings. The horned toad of our Western states shows another wonderful case of protective adap tation. The iguana of Central America and South America is among the largest of lizards, growing to a length of three feet or more. It has the distinction of being one of the few edible lizards. Snakes. Probably the most disliked and feared of all animals are the snakes. This feeling, however, is rarely deserved. Our |