Ohscrvations of Cyclo]_oea in the Human Siibjcd, etc. 277 



central position. The term Cyclopea is not, however, free 

 from objection, for the existence of a single eye is by no 

 means constant, as the group includes monsters in which 

 there are two distinct eyeballs, and others in which both are 

 absent. The Cyclopea embrace all those monsters in which 

 there is defective development of the parts derived from the 

 anterior cerebral vesicle, so that the fore-brain is not divis- 

 ible into two hemispheres, the olfactory bulbs are absent or 

 rudimentary, and the optic vesicles are more or less imper- 

 fectly divided, or even in extreme cases entirely absent. 

 Associated with the cerebral defects are changes in the nasal 

 and orbital cavities, the latter tending to unite more or less 

 completely into a single orbit, and the former to be pushed 

 upwards and forwards, and prevented from forming any com- 

 munication with the pharynx. 



Many writers maintain that we must seek for the primary 

 cause of these malformations in the defective development of 

 the anterior cerebral vesicle ; while Hannover seems disposed 

 to regard an imperfect formation of the prechordial part of 

 the base of the skull as the primary defect. There can be no 

 doubt that the malformations of these two parts — brain and 

 skull — are intimately connected with one another. We will 

 briefly refer to several points of interest suggested by our 

 examination of the condition of the skull bones. In all our 

 specimens the orbital cavity was single, although in a few 

 cases it presented faint indications of a mesial septum. The 

 proboscis, which usually exists, and is placed above the orbit, 

 is formed from the fron to-nasal process and the lateral nasal 

 processes. The cavity in its interior in the human subject (a.), 

 and in the pig (&.), evidently represented imperfect nasal 

 cavities. In consequence of the fusion of the two orbits, 

 these always terminate behind blindly, and never communi- 

 cate with the pharynx. 



JSTormally the fronto-nasal process descends to form the 

 columella of the nose, and below that it gives rise to the 

 lunula or central part of the upper lip. It is interesting, in 

 relation to this point, to notice that in the human cyclops {a.) 

 the upper lip did not possess a lunula. In connection with 

 the deeper parts of the fronto-nasal process are formed the 



