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abdominal absent adult aorta aperture archenteron artery articulation auditory capsule auricle becomes blastopore blood body bony brain branch branchial arches canal cartilage cartilaginous caudal cavity ccelome cells centrum cerebral cloaca connected consists conus arteriosus coracoid Craniata cranium dermal developed diencephalon digits distal dorsal duct ectoderm Elasmobranchs elongated embryo epithelium external Fishes fold foramen front gill-slits gills glands groove hyoid intestine investing bones kidney lateral layer limbs lobes longitudinal lower jaw lungs Mammals mandible maxilla Meckel's cartilage median medullary membrane mesoderm mouth muscles nasal nerve notochord occipital olfactory bulb optic orbit organ ossified oviduct pair palatine parietal pectoral pectoral fin pelvic fins pharynx pineal pituitary plate portion posterior end premaxilla pterygoid quadrate region renal Reptiles ribs segmentation side sinus skull spinal sternum structure tail teeth Teleostomi transverse trunk tube upper ureter urinogenital usually vein ventral surface ventricle vertebrae vertebral column wall
Page 304 - In Anura the limbs are modified by the fusion of the radius and ulna and of the tibia and fibula, and by the great elongation of the two proximal tarsals. A pre-hallux is frequently present. the lower Urodela the muscles of the trunk and tail occur in the form of typical
Page 566 - in the male, and grow from persistent pulps; both the upper and lower are bent upwards and outwards and work against one another in such a manner that the upper wears on its anterior and external surface, the lower at the extremity of the posterior surface. The
Page 488 - and the first and fifth of the pes are never longer than the others. One tooth on each side in each jaw—the last premolar in the upper jaw and the first molar in the lower—is always modified to form the carnassial or sectorial tooth with a cutting edge which bites against the edge of the opposed tooth. This sub-order comprises the Cats
Page 361 - In the Crocodilia and Chelonia, instead of the copulatory sacs, there is a median solid penis attached to the wall of the cloaca, and a small process or clitoris occurs in a corresponding position in the female. Though fertilisation is always internal, most Reptilia are oviparous, laying eggs enclosed in a tough, parchmentlike or calcified , shell. These are
Page 160 - the dorsal surface. The right eye has been removed. The cut surfaces of the cartilaginous skull and spinal column are dotted. The buccal branch of the facial is not represented,
Page 91 - br.), or sets of branchial filaments belonging to the adjacent sides of two consecutive gill-pouches. On the other hand, a gill-pouch is equivalent to the posterior hemibranch of one gill and the anterior hemibranch of its immediate successor. In some Amphibia water-breathing organs of a different kind are found. These are the
Page 171 - of the tooth. The skeleton is composed of cartilage, with, in many cases, deposition of calcareous matter in special places—notably in the jaws and the vertebral column. The entire spinal column may be nearly completely cartilaginous (Hexanchus and Heptanch-us), but usually the centra are strengthened by radiating or concentric lamellae of
Page 210 - (ba), a structure which differs from a conus in being part of the aorta, and not of the heart; its walls do not contain striped muscle, and are not rhythmically contractile. In accordance with the atrophy of the hyoid gill there is no afferent branchial artery to that arch, but a
Page 480 - The skull has two condyles for connection with the atlas, instead of the single condyle of the Sauropsida ; and the lower jaw, which consists of only a single bone on each side, articulates with the skull in the squamosal region without the intermediation of the separate quadrate element always present in that position in Birds and Reptiles.