362 



ORR. 



[Vol. I. 



EXPLANATION OF PLATES. 



IXDEX-LETTERS. 



A. Artery. 



AF. Anterior medullary fold. 



AL. Alimentary canal. 



Am. Amnion. 



Ao. Aorta. 



ar. Anterior spinal nerve root. 



CC. Canalis centralis of the medulla. 



c. Dorsal constriction in the region 



of the thalamencephalon. 

 Ch. Chiasma of optic nerves. 

 CS. Choroid slit. 

 ' CZ. Coelenteric zone. 



d. Dorsal point of union of medul- 



lary folds. 



dL. Dorsal longitudinal fibres of the 

 medulla. 



E. Ear. 



Ed. Epidermis. 



Ef. Epiblast. 



Eph. Epiphysis. 



Ept. Epitheiial wall. 



Ey. Eye. Ey" . Outer wall of eye- 

 cup. Ey' . Inner wall of eye- 

 cup. 



FB. Fore-brain. FB' , rudiment of 

 secondary fore-brain, and 

 FB", of thalamencephalon. 



^, Ganglion of spinal nerve. 



g-c. Anterior gray column. 



JIB. Hind-brain. 



HC. Head-cavity. 



Hep. Liver-rudiment. 



Hph. Hypophysis. 



HT. Heart. HTa. Atrium. HTv. 

 Ventricle of heart. 



Hyp. Hypoblast. 



in.FB. Infundibular region of fore- 

 brain. 



LF. Longitudinal fibres of walls of 

 the medullary tube; LF" , the 

 same uniting anteriorly. 



Ey. Lower jaw. 



M. Mouth. 



MB. Mid-brain. 



iii.b. Muscle-bud. 



Md. Medulla. 



' In Fig. 34, C, the index-letters CZ should 

 in the place of CZ. 



Mes. Mesoblast. 



MF. Medullary folds. 



MHp. Mass of indistinct mesoblast 

 and hypoblast. 



M.i?i. Mouth involution. 



Mp. Muscle somites. 



N. Notochord. 



Na. Nasal thickening of epidermis, 

 with rudiment of N olfacto- 

 ries adjoining. 



Ne.c. Neurenteric canal. 



NF. Nerve-fibres. 



NM. Neuromeres. NM'. Neuro- 

 meres of fore-brain. 



' «///, 7iV, etc. Third, fifth, etc., cra- 

 nial nerves. « Fj, 

 n Vo. First and sec- 

 ond branches of 

 the fifth nerve. 



0. External opening of the primary 

 first ventricle. 



CE. Qi^sophagus. 



og. Optic groove. 



Op. Wall of optic vesicle. Op' pos- 

 terior and Op" anterior wall 

 of optic stalk. 



Opv. Optic ventricle. 



O.st. Optic stalk with lumen. 



Fa7i. Rudiment of pancreas. 



EC. Pluero-pericardial cavity. 



ECs. Posterior commissure. 



E-S. Plane of section. 



ET. Pleuroperitoneal cavity. 



pfe. Ventral downgrowths of spinal 

 cord. 



EV. Protovertebrai. 



So. Somatopleure of mesoblast. 



Sp. Splanchnopleure of mesoblast. 



Spt. Neural, septa. 



T. Tail. 



TF. Transverse ventral fibres. 



T//. Thalamencephalon. 



T/ig. Thyroid gland. 



Tr. Rudiment of tracheal tube. 



V. Vein. 



vL. Ventral longitudinal fibre, 

 stand in the place of «///, and ;//// should be 



