36 The Unity of the Organism 



advanced the hypothesis that the mitochondria answer the 

 conditions of Hertwig's theory for the cytoplasmic part of 

 the male, though probably not of the female germ-cells. 

 Thus Meves reached the rather attractive conception that 

 "heredity is accomplished through protoplasm and nucleus 

 together." Were we to know no more than this about his 

 theory we might suppose his position to be that of a genuine 

 integrationist. However, his very next sentence does not 

 permit us to question any further the orthodoxy of his ele- 

 mentalism. "The qualities of the nucleus," he says, "are 

 carried over by the chromosomes, those of the plasma by 

 the chondriosomes." In other words the working together 

 of nucleus and cytoplasm which he conceives is not of the 

 sort which makes the part played by each contribute to all 

 the results, but that one set of elements produces its partic- 

 ular part of the total effects, while another set produces 

 another part of the effects. 



The Mitochondria], Theory Tested by the Ontogeny of the 

 Spermatozoa 



The utter inadequacy of this hypothesis is shown by some 

 of the same evidence which revealed to us the inadequacy of 

 the chromatin theory, namely that when we come to study 

 the histogenetic processes by which innumerable hereditary 

 attributes are produced, we find portions of the cytoplasm 

 other than the mitochondria taking the leading part in the 

 production. Perhaps no single one of the many instances 

 examined by us of cytoplasmic participation in the produc- 

 tion of attributes refutes Meves' hypothesis more complete- 

 ly and instructively than that of the developing sperm of the 

 fowl tick already described. 



We have already examined this case as one of special weight 

 in proving that the cell-body, in contradistinction to the nucleus, 

 is hereditary substance. Now we must see the conclusiveness 



