334 Charles R. Stockard 



ferent chemical conditions may each induce by their actions a 

 specific type of larva from a given variety of egg. 



SUMMARY 



1 The eggs of the fish, Fundulus heteroclitus, give rise to a 

 large percentage of cyclopean embryos when subjected during 

 their development to solutions of magnesium salts in sea-water. 

 Similar results follow if the eggs are placed in the solutions either 

 before cleavage or when in the two or early four-cell stages, later 

 stages were not tried. This is the first instance of repeatedly 

 causing, by the use of chemical substances, vertebrate monstros- 

 ities such as are known in nature. 



2 The peculiar embryos with the median cyclopean eye are 

 able to hatch. Many of them swim about in a perfectly normal 

 manner, darting back and forth to avoid objects placed in their 

 field of vision as readily as do two-eyed individuals. 



3 The cyclopean fish is exactly comparable to the monstrous 

 Cyclops of man and other mammals. Both have a median eye 

 either double or single in its structure. The nose in the mam- 

 malian Cyclops is a single proboscis-like mass above the eye. The 

 nasal pits in the "Magnesium embryos" are sometimes united 

 and sometimes separate, but the mouth hangs ventrally as a pro- 

 boscis-like organ strikingly suggesting in form the nose in mam- 

 malian cyclopia. The mouth of Fundulus normally occupies an 

 extremely anterior position but in the cyclopean fish the eye has 

 usurped this place, thus preventing the usual forward growth 

 of the mouth elements and forcing them to remain ventrally 

 as the proboscis-like mass. (See Figs. 25, 26, 27.) In cyclopean 

 mammals a similar mechanical explanation accounts for the 

 condition of the nose. The median eye obstructs the path of 

 down-growth which passes normally between the eyes, and 

 forces the nose to form above the eye as a proboscis on the fore- 

 head. 



4 A study of more than 275 living cy clops monsters and of 

 many of these in section shows all degrees in the defect. Eyes 

 unusually close together, intimately approximated eyes, the double 



