Fig. 47. — Transverse section through anterior part of head of double monster 

 belonging to Class II., i.e. the type illustrated in PI. I. fig. 6 (union at 

 medulla). Compare with the series begun in PL VIII. fig. 35 (union at optic 

 lobes). 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 

 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 PL I. fig. 6. ( x 18.) 



Fir,. 48. — Transverse section from same series as last figure, but a short 

 distance further back. Compare with PL 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 PL XXI. tigs. 91-93. 

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



PL. XIII. 



