76 The Unity of the Organism 



fish does not take any food during the period." l The work 

 of Riddle and his collaborators is producing evidence to the 

 same effect. 



Such researches do not, to be sure, prove that the chem- 

 ico-physiological changes extend to the chromosomes of the 

 germ-cells, much less to the imaginary determiners of hered- 

 ity in the chromosomes. But viewing the results in the 

 light of the well-grounded general belief that the most 

 fundamental test of living substance is metabolic change, 

 it is seen that any hypothesis which assumes the existence 

 in the germ-cells of something virtually not subject to the 

 general metabolism of the cells, assumes at the same time the 

 burden of furnishing objective evidence that such a something 

 does exist. 



As a matter of fact the prime offense of the germ-plasm- 

 determiner hypothesis is that its very essence places it 

 beyond the reach of scientific observation. Such truth as it 

 may contain cannot be made really effective because it can 

 not be proved, and such error as it may contain can not 

 be robbed of its power for evil because it cannot be dis- 

 proved. In a word, the hypothesis is one that belongs to 

 the realm of dialectics primarily, and has no just claim to 

 a place in inductive science. 



The Possibility of Changmg Sex By Influences on the Germ 



But perhaps the most conclusive evidence of the funda- 

 mental dependence of true germinal material upon the or- 

 ganism, should somewhat fuller verification of the obser- 

 vations be obtained, are results like those reached by Whit- 

 man, King, Whitney, Riddle, and by R. Hertwig and his 

 students, according to which sex may be reversed in several 

 animal species by various conditions extraneous to the 

 germ itself, acting on the germ-cells from which the animal 

 is to develop. The instance of this usually regarded as best 

 established is afforded by certain species of frogs and toads. 



