268 THE THEORY OF THE GENE 



the frog, the gonads often appear to be intermediate. The 

 classification of individuals of this sort as male or female 

 has led to much dispute. In recent years it has been 

 shown that these intermediate forms often become males, 

 and it has even been claimed that in many races all males 

 pass through this stage. 



y 





t • 



c ' •• ' . Diploid Male Eg^ 

 opermatagonia '^ 



• % *»• 





X 



•V* 



Oo^onia^ 



st 



1 SpeTmatocyte 



Fig. 144. 



Chromosome groups, spermatogonia and oogonia, and diploid male 



egg of Perla. (After Junker.) 



The experiments of Richard Hertwig have shown that 

 by delaying the fertilization of the frog's e^^g, the pro- 

 portion of males is greatly increased, and, in extreme 

 cases, all individuals become males. The attempts to cor- 

 relate these cases of retarded fertilization with chromo- 

 somal alterations have not been successful. 



