_a._ Anus. _ab._ Air-bladder. _ab´._ Aperture of air-bladder into throat. _ac._ Anterior commissure. _af._ Anal fin. _al._ Alimentary canal. _ao._ Aorta. _ar._ Artery. _au._ Auditory pit. _b._ Brain. _bc._ Body-cavity. _bd._ Bile duct. _bd´._ Aperture of bile duct into duodenum. _bl._ Coalesced portion of segmental ducts, forming urinogenital bladder. _bra._ Branchial arches. _brc._ Branchial clefts. _c._ Pyloric caæca. _c´._ Apertures of caæca into duodenum. _cb._ Cerebellum. _cdv._ Cardinal vein. _ce._ Cerebrum: in figs. 47A and B, anterior lobe of cerebrum. _ce´._ Posterior lobe of cerebrum. _cf._ Caudal fin. _cn._ Centrum. _ch._ Choroidal fissure. _crv._ Circular vein of vascular membrane of eye. _csh._ Cuticular sheath of notochord. _cv._ Caudal vein. _d._ Duodenum. _dc._ Dorsal cartilage of neural arch. _df._ Dermal fin-rays. _dl._ Dorsal lobe of caudal fin. _dlf._ Dorsal fin. _e._ Eye. _ed._ Epidermis. _ep._ Epiblast. _fb._ Fore-brain. _fe._ Pyriform bodies surrounding the zona radiata of the ovum, probably the remains of epithelial cells. _gb._ Gall-bladder. _gd._ Genital duct. _gl._ Glomerulus. _gr._ Genital ridge. _h._ Heart. _ha._ Hæmal arch. _hb._ Hind-brain. _hc._ Head-cavity. _hpd._ Hepatic duct. _hm._ Hyomandibular cleft. _hop._ Operculum. _hy._ Hypoblast; in fig. 10, hyoid arch. _hyl._ Hyaloid membrane. _ic._ Intercalated cartilaginous elements of the neural arches. _in._ Infundibulum. _ir._ Iris. _is._ Interspinous cartilage or bones. _iv._ subintestinal vein. _ivr._ Intervertebral ring of cartilage. _k._ Kidney. _l._ Lens. _lc._ Longitudinal canal, formed by union of the vasa efferentia. _lin._ Lobi inferiores. _ll._ Ligamentum longitudinale superius. _lr._ Liver. _lt._ Lateral line. _ly._ Lymphatic body in front of kidney. _m._ Mouth. _mb._ Mid-brain. _mc._ Medullary cord. _mel._ Membrana elastica externa. _mes._ Mesorchium. _mn._ Mandible. _md._ and _mo._ Medulla oblongata. _ms._ Mesoblast. _na._ Neural arch. _na´._ Dorsal element of neural arch. _nc._ Notochord. _nve._ Network formed by vasa efferentia on inner face of testis. _od._ Oviduct. _od´._ Aperture of oviduct into bladder. _ol._ Nasal pit or aperture. _olf._ Olfactory lobe. _op._ Optic vesicle. _op ch._ Optic chiasma. _opl._ Optic lobes. _op th._ Optic thalami. _or ep._ Oral epithelium. _ov._ Ovary. _p._ Pancreas. _pc._ Pericardium. _pcf._ Pectoral fin. _pch._ Pigmented layer of choroid. _pf._ Peritoneal funnel of segmental tube of mesonephros. _pfp._ Peritoneal funnel leading into pronephric chamber. _pg._ Pectoral girdle. _plf._ Pelvic fin. _pn._ Pineal gland. _po._ Primitive germinal cells. _pr._ Mesoblastic somite. _prc._ Pronephric chamber. _prn._ Pronephros. _pr n´._ Opening of pronephros into pronephric chamber. _pt._ Pituitary body. _py._ Pyloric valve. _pz._ Parietal zone of blastoderm. _r._ Rostrum. _rb._ Rib. _rc._ Rectum. _s._ Spleen. _sc._ Seminal vessels passing from the longitudinal canal into the kidney. _sd._ Suctorial disc.