Mucous groove 



Inner eye of right twin bead 



Supraorbital bar 



Rectus oc. ext. 



Cavity of cerebral lobes 



Olfactory cartilage 



Olfactory nerve and pit 

 Rectus oc. internus 

 Obliq. inf. of outer eye 

 Palato-pterygoid 

 Rectus oc. inf. 



Trabeculae cranii 



Inward dip of surface epithelium 

 Commencement of an inner or adjacent lower lip 

 Anterior ends of united inner Meckel's bars 



The two adjacent eyes are cut through in their posterior halves, near the 

 places of entrance of the optic nerves. The anterior ends of the cerebral lobes 



lobes). 



belonging to both heads are seen in oblique section, as are also various skeletal 

 elements and ocular muscles. For plane of section see PL XXI. figs. 91-93, 

 line 47. Other references are given under PI. I. fig. 6. ( x 18.) 



^% 



"Commencement of optic lobes 



Supraorbital bars 



Pineal body 



Rectus oc. ext. 



Rectus oc. sup. 



Cerebral lobes 



Olfactory cartilage 



Rectus oc. int. 



Olfactory organ 

 -Obliq. oc. inf. of outer eye 

 -Trabeculae cranii 

 Palato-pterygoid cartilage 



- An inner lower lip 



Anterior end of united inner hyomandibulars 

 Upper end of united inner Meckel's cartilages 

 Inward dip of surface epithelium 



Fu;. 48. Transverse section from same series as last figure, but a short 

 distance further back. Compare with PI. III. fig. 13 (normal). The section 

 passes through the posterior portions of the adjacent eyes, and through the 

 extreme anterior part of the composite otocyst which represents the fused 

 adjacent auditory organs of the twin heads. The outer eyes lie some distance 

 behind the plane of the section, which is indicated by line 48 in PI. XXI. figs. 91-93. 

 Other references are given under PI. I. fig. 6. ( x 18. ) 



J. F. G. 



PL. XIII. 



XIII 



