_al._ Alimentary canal. _ao._ Dorsal aorta. _auv._ Auditory vesicle. _bd._
Formative cell probably derived from the yolk. _cav._ Cardinal vein. _ch._
Notochord. _ch´._ Thickening of hypoblast to form the notochord. _eb._ Line
indicating the edge of the blastoderm. _ep._ Epiblast. _ep´._ Epidermis.
_er._ Embryonic rim. _es._ Embryonic swelling. _gl._ Glosso-pharyngeal
nerve. _h._ Head. _ht._ Heart. _hy._ Hypoblast. _ll._ Lower layer cells.
_ly._ Line of separation between the blastoderm and the yolk. _m._
Mesoblast. _mc._ Medullary canal. _mg._ Medullary groove. _mp._
Muscle-plate. _mp´._ Early formed mass of muscles. _n._ Peculiar nuclei
formed in the yolk. _n´._ Similar nuclei in the cells of the blastoderm.
_na._ Cells which help to close in the alimentary canal, and which are
derived from the yolk. _ny._ Network of lines present in the food-yolk.
_ol._ Olfactory pit. _op._ Eye. _ov._ Oviduct. _pn._ Pineal gland. _pov._
Projection which becomes the ovary. _pp._ Pleuro-peritoneal cavity. _pp´._
Remains of pleuro-peritoneal cavity in the head. _prv._ Protovertebræ.
_pwd._ Primary points of involution from the pleuro-peritoneal cavity by
the coalescence of which the Wolffian duct is formed. _sg._ Segmentation
cavity. _so._ Somatopleure. _sos._ Stalk connecting embryo with yolk-sac.
_sp._ Splanchnopleure. _spn._ Spinal nerve. _sur._ Suprarenal body. _ts._
Caudal lobes. _v._ Blood-vessel. _vg._ Vagus nerve. V. Fifth nerve. VII.
Seventh nerve. _vc_, 1, 2, 3, &c. 1st, 2nd and 3rd &c. visceral clefts.
_vp._ Vertebral plates. _wd._ Wolffian duct. _x._ Peculiar body underlying
the notochord derived from the hypoblast. _yk._ Yolk spherules.
All the figures were drawn with the Camera Lucida.