228 



Biology in America 



which Professor Wilder calls ' ' cosmobia. ' ' Thus in man there 

 exists a whole series of duplicities from a slight cleft of the 

 spinal cord to those in which the cord is doubled for its entire 

 length and is more or less rudimentary. The doubling 

 process may go further, resulting in a double-headed monster, 

 or one with .two heads and four arms. Or if the process 

 proceed in the reverse direction a single body and head may 

 possess two pairs of legs; while if the doubling process occur 

 at both ends simultaneously "Siamese twins" result; until 

 finally if the body be completely separated "identical twins" 



r 



\ 



CYCLOPEAN FISH 



Produced by treatment with magnesium salts. From Stockard, in 

 1 ' Journal Experimental Zoology, ' ' Vol. 6. Mouth ; yolk sack. 



occur, which are always of the same sex, and resemble each 

 other as closely as the proverbial "two peas in a pod." 



The experiments on fish embryos strongly support the 

 theory of Mall, that monstrosities in man are due to diseased 

 conditions in the mother's uterus, with resultant metabolic 

 disturbances and the formation of toxins in the embryo and 

 fetus. 



We have seen in the last chapter that our present evidence 

 very strongly indicates that sex is predetermined in the egg, 

 so that most of the supposed instances of its artificial control 

 are at the present time of historical interest only. One of the 

 most popular theories of sex determination ascribes to food a 

 sex determining influence. Experiments of this nature have 



