_a_, head-fold of amnion. _aa_, anterior appendage. _ac_, anterior cardinal vein. _aip_, anterior intestinal portal. _al_, allantois. _an_, anterior nares. _ao_, aorta. _ar_, aortic arch. _au_, auricle. _b_, bulbus arteriosus. _bc_, body cavity. _bd_, bile duct. _bd'_, opening of bile duct to liver. _bd''_, opening of bile duct to duodenum. _blp_, blastopore. _bp_, basilar plate. _bs_, bile-sac. _bv_, blood vessel. _c_, centrum of vertebra. _ca_, caudal artery. _ce_, caecum. _ch_, cerebral hemisphere. _cl_, cloaca. _cm_, circular muscle layer. _cn_, cranial nerve. _cp_, posterior choroid plexus. _cv_, cardinal vein. _d_, duodenum. _dc_, ductus Cuvieri. _di_, diverticulum of stomach. _e_, eye. _ec_, ectoderm. _ec'_, thickening of ectoderm. _en_, entoderm. _en'_, endocardium. _ent_, enteron. _ep_, epidermal layer of ectoderm. _ep'_, epithelium. _epi_, pineal body. _es_, embryonic shield. _f_, fronto-nasal process. _fb_, forebrain. _fg_, foregut. _g^1-5_, gill clefts. _gf^1-6_, gill folds. _gl_, glomerulus. _h_, head-fold. _gs_, glottis. _gz_, gizzard. _hb_, hindbrain. _hc_, head cavity. _hg_, hindgut. _ht_, heart. _i_, intestine. _i'_, stomach. _il_, large intestine. _in_, infundibulum. _io_, intromittent organ. _ir_, iris. _it_, iter. _k_, kidney. _la_, larynx. _li_, liver. _lm_, longitudinal muscle layer. _ln_, lens. _lp_, _lp'_, etc., loops of intestine. _lu_, lungs. _lv_, lens vesicle. _m_, mouth. _ma_, manus. _mb_, midbrain. _me_, medullary canal. _me'_, tip end of medullary canal. _md._, mandibular folds. _mes_, mesoderm. _mes'_, myocardium. _mf_, medullary fold. _mg_, medullary groove. _mk_, Meckel's cartilage. _ml_, muscle layer. _mp_, muscle plate. _ms_, mesentery. _mv_, meatus venosus. _mx_, maxillary fold. _myc_, myocoel. _n_, nasal cavity. _na_, neural arch of vertebra. _nc_, neurenteric canal. _nl_, nervous layer of ectoderm. _nt_, notochord. _o_, ear vesicle. _oc_, optic cup. _oe_, oesophagus. _on_, optic nerve. _os_, optic stalk. _ov_, optic vesicle. _p_, pituitary body. _pa_, posterior appendage. _pag_, post-anal gut. _pan_, pancreas. _pan'_, opening of pancreas. _pc_, posterior cardinal vein. _pe_, pes. _pg_, primitive groove. _ph_, pharynx. _pip_, posterior intestinal portal. _pl_, pelvis. _pn_, posterior nares. _pr_, pericardial cavity. _ps_, primitive streak. _pt_, pecten. _py_, pylorus. _r_, rib. _rt_, retina. _s_, somites. _sc_, spinal cord. _se_, spenethmoid cartilage. _sg_, spinal ganglion. _sl_, submucosa. _sm_, splanchnic mesoblast. _sn_, spinal nerve. _so_, somatic mesoblast. _st_, stomodaeum. _sy_, sympathetic nervous system. _t_, tail. _ta_, trachea. _tg_, thyroid gland. _tn_, tongue. _to_, tooth anlage. _tr_, trunchus arteriosus.