TYPES OF VERTEBRATE AND INVERTEBRATE EYES 31 



Fig. 23. — Cephalo-thoracopagus Monosymmetros (Duplicitas Posterior). 

 (Redrawn from Schwalbe.) 



A and B, the same specimen viewed from opposite sides. The letters Y and Z 

 denote the individual components of the twin monster, and the letters / and r 

 the left or right side. A, complete "secondary" face, Y r Z 1 ; B, in- 

 complete " secondary " face Z r Y 1 showing a single palpebral aperture and 

 fused eyelids covering a cyclops eye. The nose and mouth are absent and the 

 ears approximated. 



