Soft tissues of upper jaw 



- Soft tissues of lower jaw with germs of teeth 



Glossohynl 



Hypohyal 



" " 'Copula, visceral arch III 



^'Meckel's cartilage (visceral arch 1) 

 Ceratohyal 



Meckel's cartilage 

 ..- Ceratohyal 



, I, II, III 

 " Truncus arteriosus 

 Ventricle of heart 

 Auricle of heart 



Inferior cardinal veins 



Gill cover 



Cartilage of pectoral fin 



Yolk 



Pancreatic tissue and bile ducts 



........ The two intestines just beyond the stomachs 



....-- Single portion of intestine formed by junction 

 of the two former 



.Wolffian body 

 . .The two notochords 



^^\ Mesial muscular mass 



Lateral muscles 



FIG. 54. Horizontal section belonging to the same s'-ta-s as the hi^t, 

 but at a distinctly deeper level. Some of the gill-arch structures are seen 

 in either head in front, and behind these certain chambers of the double 

 heart, which lies inside a single large pericardia! cavity. The alimentary 

 canals are double down to the level of the stomach. Two bile ducts enter 

 the first part of the composite intestine. For references see under PI. II. 



fig. 7 . (X20.) 



X. 



FIG. 55. Horizontal section furthe 

 Tlie section passes through tlv 

 the place of union. The spii. 

 section is drawn out trnnw-i 

 distal section is a!> 

 The mesial m 



and is seen to be < ; tenet 



two outer series of mu- 

 neural arch cartilages 



(X28.) 



... Composite spinal cord, much drawn out 



transversely 

 "" The two notochords 



Inner neural arch cartilages 



Haemal arch cartilages 



......... Aortae 



......... Wolffian bodies 



""Mesial muscular mas-, 

 " Lateral muscles 



-...."'The two notochords 



Spinal cord 



rs the last. 



body behind 



!s proximal 



while the 



1 i itochords. 



here, 



ing with the 

 ie adjacent 

 ' II. fig. 7- 



J. F. G. 



PL. XVI. 



XVI 



