236 SCIENCE AND PHILOSOPHY OF THE ORGANISM 



pure maternal type. This experiment seems to place the 

 morphogenetic importance of protoplasm beyond all doubt. 



I should prefer not to make any definite statement 

 about our problem at present. Our actual knowledge 

 of the organisation and metabolism of both nucleus and 

 protoplasm is so extremely small and may relate to such 

 very insignificant topics, that any definite decision is im- 

 possible. I myself believe that the nucleus plays an 

 important part in heredity, perhaps even a greater one 

 than protoplasm, but this is only my belief. 1 



The discovery of Gruber and others, that Protozoa are 

 only capable of restitution if they contain at least a frag- 

 ment of the nucleus, has also been used occasionally as a 

 proof of the morphogenetic importance of the nucleus. But 

 might not this absence of restitution where nuclear 

 material is lacking be understood equally well on the 

 hypothesis of Loeb and K. S. Lillie that the nucleus is a 

 centre of oxidation in the cell ? Eemove the heart from 

 a vertebrate and the animal will not digest any more ; but 

 in spite of that the heart is not the organ of digestion. 



And so we lay stress once more upon this point : that 

 the experimental results of hybridisation and the analytical 

 results obtained by the discussion of the complex- 

 equipotential systems are of greater value to the theory 

 of heredity than all speculation about the importance or 

 unimportance of special constituents of the cell, of whose 

 organisation, chemistry, and physics, scarcely anything is 

 known at present. 2 



1 Surely the new results of Herbst, mentioned above, are another indication 

 of the importance of something in the nucleus. The first stage in partheno- 

 genesis, which he used in his experiments, is a nuclear phenomenon. 



2 Boveri (Ergcbn. ub. d. Konstitution etc. des Zellkerns, Jena, 1904 ; 



