FIG. 49. Transverse section from the same series as Figs. 47, 48. hut through 

 the outer eye>, tin- optic lobes, and the hyoinandibular suss a the inner 



or adjacent sides of the twin heads. Below, in the middle line, is the v 

 bf-tw > mouth-openings, and in it the inner or adjacen 



cartil i moulding of the adjacent united periotie capsules and 01 



otocysts is extremely interesting. See also the two following figures. ( 

 references are given under PI. I. fig. 6, and the plane of section is indicat. 

 line 49 in PI. XXI. figs. 91-93. ( X 18.) 



The 



Semicircular canals of inner 

 compressed double otocyst 

 "" Optic lobes 

 -Periotie cartilage 

 -Supraorbital bar 



-Infundibulum 

 J','"Rectus oc. sup. 



,i\- Inner recti near their origins 



I-IJ+- Rect. int. outer eye 



'I- Rect. inf. outer eye 



"Palato-pterygoid 



"' Trabeculae cranii 



Periotie cartilage (composite) 

 United adjacent hyomandibulars 

 United adjacent hyoids 



two adjacent Meckel's cartilages in the septum between 

 the two mouth openings 



Semicircular canals of inner compressed double octocyst 



Optic lobes 



-The two utricles, here separate 



Iter 



.Supraorbital bar 

 - Rectus oc. sup. 

 .-Cavity of hypoarium 



|- Floor of periotie capsule 

 *!- Trabeculae cranii 

 W--)-Rect. inf. outer eye 

 /- Palato-pterygoid 

 " 'United adjacent hyoids 



An outer Meckel's cartilage 



The two adjacent Meckel's cartilages in the septum between 

 the two mouth openings. 



FIG. y Transverse 



fr. 



through the posterior part ni the " 



inner hyixwna, the entrance of the optic nerve on one side, a 

 the mesial oral septum containing the united adjacent hyoi 

 und-r PI. I. fig. 6. (x 18.) 



r ittr, the 

 ck part of 

 leferences 



FIG. 51. TransvetS' 1 

 through the outer auditory organs . 

 obviously made up of two converg 

 the inner parachordals i 'I mesia 



them. Compare this section . 

 (union at optic lobes) Other lefcieiiuts unc 



I". XXI. !i!v ',1-9: 



Mesial muscular mass 



Medulla (almost double) 



Parts of inner composite labyrinth 

 United inner jugular veins 



Periotie capsule 



Parts of an outer labyrinth 



Ganglion, auditory nerve 

 Parachordal cartilages 



Notochord 



Hyomandibular 



Upper end, visceral arch III 



(ist branchial) 

 Aortic arch and roots 



Visceral arch IV 



Visceral arch V 



Copula arch V 



"""- Hyoid cartilage (an outer arch) 



Truncus arteriosus 



Irregular septum between the two mouth openings 

 rh* < but 



i, which is 



notochord is double, and 

 ass of muscle wedged in between 

 ial), and with PI. IX. fig. 38 

 'I. I. fig. o, and plane of sectio? 



J. F. G. 



PL. XIV. 



XIV 



