. A civic biology : presented in problems. Biology; Sanitation. ANIMALS CLASSIFIED 185. A common snail, a mollusk. (From a photograph by Davison.) than the worms and may be known by the spines in their skin. Starfish or sea urchins are examples. VI. Arthropods. - These animals are distinguished by having jointed body and legs. They form two great groups. The higher forms of the Crustacea have only two regions in the body, a fused head and thorax, called the cephalothorax, and an abdominal region. A second group is the Insecta, of which we know some- thing already. Crustacea breathe by means of
. A civic biology : presented in problems. Biology; Sanitation. ANIMALS CLASSIFIED 185. A common snail, a mollusk. (From a photograph by Davison.) than the worms and may be known by the spines in their skin. Starfish or sea urchins are examples. VI. Arthropods. - These animals are distinguished by having jointed body and legs. They form two great groups. The higher forms of the Crustacea have only two regions in the body, a fused head and thorax, called the cephalothorax, and an abdominal region. A second group is the Insecta, of which we know some- thing already. Crustacea breathe by means of gills, which are structures for taking oxygen out of the water, while adult insects breathe through air tubes called trachea. Two smaller groups of arthropods also exist, the Arachnida, consisting of spiders, scorpions, ticks, and mites, and the Myriapoda, examples being the " thousand leggers' found in some city houses. VII. Mollusca. - -Another large group is the Mollusca. This phylum gets its name from the soft, unsegmented body (mollis • •• soft). Mollusks usually have a shell, which may be of one piece, as a snail, or two pieces or valves, as the clam or oyster. VIII. The Vertebrates. - - All of the animals we have studied thus far agree in having whatever skeleton or hard parts they possess on the outside of the body. Collectively, they are called Invertebrates. This exoskeleton differs from the main or axial skeleton of the higher animals, the latter be- ing inside of the body. The exoskeleton is dead, being secreted by the cells lining the body, while the endo- skeleton is, in part at least, alive and is capable of growth, a broken arm or leg The skeleton of a dog; a typical vertebrate. bone will grow to-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Hunter, George W. (George Will
Size: 1358px × 1839px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., boo, bookpublishernewyorkamericanbookcompany, booksubjectbiology
