ORIGIN OF MONSTERS 535 



anlagen of the mouth, olfactory pits and the eyes of both sides 

 would in this way be brought into more or less close approxima- 

 tion or even into contact. Various degrees of the synophthalmic 

 deformitj' would thus eventually result from the more or less 

 complete union of both ophthalmoblastic areas. Incidentally 

 the elimination of parts of the area potentially representing the 

 mouth and olfactory pits will by fusion of their reimiants lead 

 to the formation of an elongated, more or less pointed mouth — 

 the 'proboscis' — and to fused olfactory pits. 



A few words would now seem necessary regarding the size of 

 the eliminated fragment r.nd the distances between the respec- 

 tive organoblastic areas of both sides. While in our diagram, 

 by which only a very rough portrayal of the presumable condi- 

 tions is attempted, the eliminated area is relatively large and the 

 respective organoblastic areas are pretty far apart, it is not at 

 all meant to convey the idea that they are so in reality. Con- 

 cluding from w^hat appears to be lacking in the developed embryo 

 and considering the fact that growth is an increase in volume, 

 this destroyed anterior part of the head primordium must be 

 conceived of as being relatively very small in size. It follows 

 from these considerations that the bilateral ophthalmoblastic 

 areas are at this stage relatively much nearer each other than 

 they would be at a somewhat later stage, e.g., in the embryonic 

 shield. Granting this, however, it is easy to account for the fact 

 that the cyclopean eye is often much smaller in size than the 

 normal eye. For, at this stage the eliminated area may often 

 contain besides the potential interocular area a whole ophthalmo- 

 blastic area of one side and a part of the same area of the other 

 side. The remnant of ophthalmoblastic material may develop 

 laterally (monophthalmia asymmetrica) or into the median, 

 genetically single eye of perfect cyclopia, if, owing to subsequent 

 regulation it has come to occupy a median position. In the case 

 of a small cyclopean, genetically synophthalmic (i.e., 'fused') 

 eye it might be imagined that the destroyed 'wedge' of tissue 

 contained a great deal of both ophthalmoblastic areas and that 

 the remnants have, after fusion, developed into a median eye 

 smaller in size than the normal eye. However, although I do 



