268 THE THEORY OF THE GENE 



eggs (Fig. 148). The eggs have been deposited and 

 fertilized and observed to develop. There can be here 

 no doubt but that a female has arisen after removal 

 of the testes, but whether the individual operated upon 

 is to be called a male or an hermaphrodite is perhaps a 

 question of definition. Personally, I should call the above 

 toad a male, and interpret the result to mean that a male 

 has been transformed into a female by removal of the 

 testes. It seems to me a matter of secondary importance 

 that the male toad carries an organ whose cells are poten- 

 tially capable of developing into egg-cells, for, in general, 

 even when sex is determined by a chromosomal mecha- 

 nism, there is no implication that under changed condi- 

 tions undifferentiated cells situated in that part of the 

 body where the gonads develop might not become egg- 

 cells even with the chromosomal complex that gives rise 

 to a male under other circumstances. In terms of genes, 

 this means that in the toad the balance of the genes is 

 such that under the normal conditions of development 

 one part of the gonad (the anterior end) begins to de- 

 velop into an ovary, while another part (the posterior 

 end) begins to develop into a testis. The latter overtakes 

 the former as development proceeds and holds its further 

 development in check. If the testicular end is removed, 

 however, this control is lost, and the cells of Bidder's 

 organ proceed to develop into functional eggs. If this 

 interpretation is correct and if a sex-chromosomal mecha- 

 nism is present in toads (which has not as yet been 

 certainly demonstrated), the mature eggs that come from 

 Bidder's organ should have the same chromosomal com- 

 plexes (possibly an X- or a Y-chromosome each) as have 

 the ripe sperm of the male. Crossed to a normal male the 

 offspring would then be 1 XX+2 XY+1 YY. If the YY 

 embryo fails to develop there should be twice as many 

 sons as daughters. 



