352 



H. EDGEWORTH 



i. e. behind the sixth gill-clefts. No observer made mention of 

 any subsequent backward shifting of the larynx. 



I find that there is a slight trace of the laryngeal outgrowth 

 in a 10-5 mm. embryo, but it is quite clear in a 11 mm. embryo 

 (Text-fig. 10) as a median ventral outgrowth of the pharyngeal 

 and oesophageal epithelium, extending from the anterior border 

 of the fifth to 8 /Lt behind the posterior border of the sixth gill-cleft. 



Text-fio. 28. 



cled.hj'LLm 



cLedkrum -'^^''^'"' 



prunord.of 

 Sabarc ve/ttr v 

 and CLejxio-bixx/ich 



Cej-atobn v 



4] 



'cdobr, 



coraco- scop. 

 Embryo 16 mm. 



Model of Ceratobranchialia and Subarcualis 

 rectus v.i 



In a 12 mm. embryo the continuity of the laryngeal epithelium 

 with the pharyngeal and oesophageal epithelium extends from 

 16 /x in front of the anterior border of the sixth gill-cleft to 72 /x 

 behind it. In a 13-5 mm. embryo the continuity extends from 

 72 fc behind the sixth gill-cleft to 152 /x behind it. In a 20 mm. 

 embryo it extends from 480 yu behind the sixth gill-cleft to 600 u 

 behind it, and the oesophagus opens into the stomach 140 /x 



^ In Text-figs. 28 and 29 only the front parts of the Cleithrum and 

 Coraco-scapulare are represented. The epibranchialia i-iv are not shown. 



