Artificially Produced Cyclopean Fish 29 1 



of salts In distilled water where the final pressure was less than 

 that of sea-water, the normal medium of the eggs. It is also true 

 that if such substances as the sugars be added to a salt solution, 

 a smaller dose of the salt becomes effective in the presence of the 

 sugar. Morgan ('06) first called attention to this pecuhar 

 fact in studying the effects of solutions upon developing frogs' eggs. 

 This would seem to indicate that the effects were due to osmotic 

 pressure conditions and by shghtly raising the pressure with 

 another element the effective agent was assisted in its action, but 

 my lithium experiments (1906 and 1907b) are against such a view. 



A number of mixtures of MgS04 and NaCl were tried, all giv- 

 ing negative results. Mixtures of Mg(N03)2 and NaCl as fol- 

 lows were used: ^ M + J M, y\- M + | M and y ,7 M + \ m. 

 The first two caused eggs to develop cyclopia. These are mix- 

 tures closely similar to the effective MgClz and NaCl solutions. 



We conclude that cyclopean monsters are produced in Fundulus 

 eggs by the action of sea-water solutions of MgClj, Mg(N03)2 

 and mixtures of MgCl^ and NaCl and Mg(N03)2 and NaCl. 

 No other solutions of the many I have tried during three summers 

 gave similar effects. Other salt solutions and sugar solutions 

 exerting practically the same osmotic pressure also fail to cause 

 cyclopia. 



Another argument opposed to the view that osmotic pressure 

 is the cause is the fact that Fundulus embryos are so resistant to 

 changes in pressure. Since two Mg salts give similar results 

 when used in sea-water solutions, it seems probable that the 

 action of Mg, either directly or indirectly, is responsible for the 

 result. Eggs have been subjected to this action before the first 

 cleavage, during the two-cell stage and just before going into four 

 cells, with similar results. No attempt was made to determine 

 at how late a stage the cyclopean condition could still be caused, 

 though it could doubtless be induced after the eggs had passed 

 much beyond the four cell stage. The fact is that cyclopia may be 

 caused in an egg which has started its development normally and 

 which would have given a two-eyed embryo. The idea of a 

 germinal origin of the defect in this case seems excluded. Cyclopia 

 in this instance is the result of unusual external conditions. 



