286 Charles R. Stockard 



times points in a direction which would indicate that these factors 

 may be largely modified in their influences by the external con- 

 ditions. 



Most monstrosities or abnormalities in development are due 

 to the action of external factors, either mechanical, as pressure, 

 or chemical. Mammals, birds and reptiles, with their complex 

 embryonic membranes, offer many opportunities for the produc- 

 tion of secondary abnormalities arising from unfavorable mechan- 

 ical or physical conditions. Fcetal amputations and scars, mem- 

 brane fusions distorting facial development, and many other such 

 deformaties are in most cases probably due to secondary influences 

 on development. Besides these there are deformities of a dif- 

 ferent nature, such as the excessive monsters, monstra in excessu, 

 in which certain organs have over developed or produced super- 

 numerary parts; and contrasted with them are defective monsters 

 which fail to complete themselves and are therefore less than a 

 normal individual. It is with this latter class, monstra in defectu, 

 that the present study is concerned. These defective individuals 

 may be grouped into two sub-classes: first those in which certain 

 organs fail to complete themselves, as in cleft palate, hare-lip, 

 arrests in the development of the heart and other parts of the 

 circulatory system. Second, individuals in which certain paired 

 organs occur singly or without mates. True Cyclocephali or 

 Cyclops monsters find their place in this last group. 



Cyclops monsters have long been known to occur in man and 

 other mammals and are described in many of the earliest medical 

 works. In these beings the one eye is in the middle line of the 

 face and often shows external evidence of a double composition. 

 The nose which normally arises above the eyes and grows down 

 between them as the face develops is here mechanically prevented 

 from descending by the presence of the median eye in its path. 

 The foetus, therefore, has a proboscis-like nose above the eye. 

 The brain and other parts of the body are sometimes deformed 

 though they may be normal. 



Among the lower vertebrates true cyclops monsters have been 

 recorded by Spemann ('04) as resulting from mechanical injuries 

 to the eggs of the amphibian, Triton taeniatus. These mon- 



