330 Charles R. Stockard 



DISCUSSION AND CONCLUSIONS 



The foregoing facts furnish important information as to the 

 cause and manner of development of cyclopia, and the facts bear 

 directly on previous ideas concerning this subject. 



By treating the fish eggs with magnesium solutions, it is conclu- 

 sively shown that the experimenter has the power without mechan- 

 ically injuring the egg or embryo to cause what would have been 

 a two-eyed individual to become a cyclopean monster. This 

 undoubtedly is a case of the occurrence of cyclopia through the 

 action of external influences on the developing egg. I conclude, 

 then, that cyclopia does not necessarily result from germinal varia- 

 tions, but I make no claim that it may never arise in such a way. 

 On the contrary, there is no reason why cyclopia should not occur 

 through germinal variations as readily as does any other new fea- 

 ture. The fact that mammalian cyclopean monsters do not sur- 

 vive, or even if it be proven that the free-swimming cyclopean fish 

 are incapable of living or reproducing, does not argue against the 

 possibility that cyclopia may in cases be due to germinal variation. 

 Such a statement is emphasized by a case I ('07c) recently recorded. 

 In a flock of sheep in North Carolina two entirely legless lambs 

 appeared in the spring of 1907. Again in 1908 two other similar 

 lambs have occurred, one being the ofi^spring of a mother which 

 had previously borne a legless individual. These lambs were 

 unable to feed without assistance and in nature would doubtless 

 have died shortly after birth, but their peculiar occurrence in this 

 flock is very probably due to germinal variations, either within 

 the mother or father, or both. Students of inheritance consider 

 sports to be due to germinal variations and the ability of such 

 sports to survive depends merely on their adaptations to the sur- 

 roundings and not in the least on their manner of origin. No 

 reason can be given why a cyclopean individual might not occur 

 as a sport due to sudden germinal variations. From the experi- 

 ments contained in the present paper, however, it may be emphat- 

 ically afl&rmed that cyclopia is not always due to germinal origin. 



Spemann ('04) through an ingenious method of experiment, 

 produced double-headed Triton embryos which exhibited various 



