The Development of the AUigator 337 



The origin of the hypophysis and paraphysis is 

 cleariy seen; the latter projects backward. 



No connection can be seen between the first 

 rudiments of the sympathetic nerves and the cen- 

 tral nervous system. 



The lumen of the oesophagus is for a time obliter- 

 ated as in other forms. 



The choroid fissure is a very transitory but well- 

 marked feature of the eye. 



LETTERING FOR ALL FIGURES ON PLATES VI.-XXVIII. 



a, head-fold of amnion. 

 aa, anterior appendage. 

 ac, anterior cardinal vein. 

 al, allantois. 



an, anterior nares. 

 ao, aorta. 

 aop, area opaca. 

 ap, area pellucida. 

 ar, aortic arch. 

 au, auricle. 



b, bulbus arteriosus. 

 be, body cavity. 

 blp, blastopore. 



bp, basilar plate. 

 bv, blood-vessel. 



c, centrum of vertebra. 

 ca, caudal artery. 



ch, cerebral hemisphere. 

 cl, cloaca. 

 en, cranial nerve. 

 cp, posterior choroid plexus. 

 cv, cardinal veins. 

 de, ductus Cuvieri. 

 e, eye. 



ee, ectoderm. 



ec', thickening of ectoderm. 

 en, entoderm. 

 22 



en', endocardium. 



ent, enteron. 



ep, epidermal layer of ectoderm. 



epi, paraphysis. 



es, embryonic shield. 



/, fronto-nasal process. 



fb, forebrain. 



fg, foregut. 



g'-5, gill clefts. 



g/'-^ gill folds. 



gl, glomerulus. 



h, head -fold. 



hb, hindbrain. 



ht, heart. 



i, intestine. 



i', stomach. 



in, infundibulum, 



ir, iris. 



it, iter. 



k, kidney (metanephros). 



/, remains of groove between 



secondary folds. 

 la, larynx (cartilages of). 

 li, liver. 



//, lower lid of eye. 

 In, lens. 

 Ir, inferior rectus muscle of eye. 



