Nictitating membrane, 144 Notochord, 236, 238, 245, 248, 249, 251, 255, 256, 260, 263, 266, 269, 270, 285, 295, 306, 335 Nuchal shield, 47 Obex, 133 Oblique muscles, 146 Odontoid process, 52, 54 Œsophagus, 151, 152, 324, 330 cilia of, 174 epithelium of (feeding), 173 epithelium of (hibernating), 172 histology of, 168 transsections of (figures), 169, 170 Okefinokee, 10, 226 Olfactory bulb, 132, 133 Olfactory lobes, development of, 332 Olfactory tract, 132, 133, 134 Olivary enlargement of œsophagus, 151 Optic chiasma, 134 cup, 302, 309, 310, 321 lobes, 132, 133, 135 nerve, development of, 321 stalk, 302 tracts, 134 vesicle, 274, 276, 282, 294 Oral cavity, 150 Ora serrata, 147 Osteolæmus tetrapis, 3 Otic vesicle, _see_ Auditory vesicle Outer ear, 148 Ova, 193 Ovary, 193 Oviducts, 156, 193, 194 Palm Beach, Fla., 9 Pancreas, 154 development of, 326 Papillæ of tongue, 150 Paraphysis, 132, 133 development of, 319, 320, 330 Pecten, 147, 321 Pectoral girdle, 81 Penis, shaft of, 194 Pericardium, 323 Periotic capsule, 73 Pes, 317, 318, 329 Petromyzon marinus, 157 Pharynx, development of, 277, 285, 292, 295, 299 Pigment, 333, 334 Pineal body, 132, 319 Pits in scales, 49 Pituitary body, _see_ Hypophysis Plover and crocodile, 40 Posterior cardinal vein, development of, 298 Postorbital bar, 60 Prickle cells, 49 Primitive groove, 246, 249, 250, 256, 265, 267 Primitive spinal column, 326 Primitive streak, 233, 240, 246, 249, 250, 256, 265, 267, 275 Procœlia, 1 Pulp cavity of tooth, 65 Pupil, 146 Recessus cavi tympani, 149 Recessus scalæ tympani, 149 Rectum, 155 transsection of (fig.), 186 Rectus muscles of eye, 146 development of, 332 Respiratory organs, 197, 200; (fig.), 198 Rete Malpighii, 48 Retina, 147 development of, 321 Retractor oculi muscle, 146 Ribs, 77 Rima auditoria, 148 Ring muscle, 157 Roof of mouth, 165 covering of (fig.), 166 glands of, 167 papillæ of, 167 Saccus naso-lachrymalis, 146 Scales, development of, 333 Sclera, 146 Scutes, 47 Semicircular canals, 149 Semilunar valves of stomach, 154 Sexual characteristics, 19 Sexual maturity, 17 Shell membrane, 228 Shell-tooth, 334 Sinus venosus, 202 Size of alligator, 16 at hatching, 16 Skeleton, 46, 50 Skin, 87 Skull, 58 dorsal aspect of, 59 lateral aspect of, 67 posterior aspect of, 70 sagittal section of, 72 ventral aspect of, 63 Smaller part of stomach, 153 Small intestine, 154 histology of, 179, 186 mucosa of (fig.), 184 transsection of (figs.), 181, 182, 183, 185 Smithsonian Institution, 226, 227 Somatapleure, 279 Somites, 251, 252, 256, 266, 267, 274, 282, 292, 300 Special sense organs, 144