28 THE GERM-PLASM 



as vacuoles and chlorophyll bodies — pass directly from the 

 egg-cell into the daughter-cells, although this cannot by any 

 means be considered as proved. In any case such a direct 

 transmission plays only a very insignificant part in plants, and 

 practically none at all in animals, for specific structures are 

 not present in the egg-cells of animals : there may at most be 

 deposits of nutrient material. These, however, are not living 

 structures of the cell, but only passive chemical substances. So 

 far from denying that the nucleus contains the hereditary sub- 

 stance, de Vries bases his whole theory on this incontestable 

 fact. The last doubts on this point were dispelled by the ex- 

 periments of Boveri,* who, after artificially removing the nucleus 

 from the eggs of a species A of sea-urchin, and then pouring 

 over them the sperm of another species B, found that these eggs 

 developed into larvae of the latter species. In this case there- 

 fore the substance of the maternal germ-cell acted as nutrient 

 material only, whilst the paternal germ-cell impressed the char- 

 acter of the species on the larva. None of the maternal specific 

 characteristics were transmitted, and in this case, at all events, 

 the question of any '■ heredity apart from the nucleus ' is therefore 

 excluded. 



Several objections have been recently raised to my view that 

 the nucleus is the seat of heredity. Verworn,t for instance, 

 repeats the opinion, previously expressed by Whitman, that the 

 cell-body, quite as much as the nucleus, must be looked upon as 

 the hereditary substance, because the nucleus cannot exist with- 

 out the cell-body ; and also because, in his opinion, which is 

 undoubtedly a correct one, the life of a cell consists in a con- 

 tinual interchange of substance between the cell and the nucleus. 

 But is the question as to whether the closest physiological rela- 

 tions exist between the nucleus and the cell, so that neither can 

 exist apart from the other, synonymous with that as to whether 

 the hereditary substance is contained in the nucleus or in the 

 cell-body? We must at least be allowed to make the hypothesis 

 that the ' store of the primary constituents ' (' Anlagenmagazin ') 

 of the hereditary substance is contained and preserved in the 



* Boveri, ' Ein geschlechtlich erzeugter Organismus ohne miitterliche 

 Eigenschaften.' Gesellsch, f. Morph. u. Physiol., Miinchen, i6 Juli 1883, 



t Max Verworn, ' Die physiologische Bedeutung des Zellkerns,' Bonn, 

 1891 (Archiv. f. ges. Physiol., Bd. 51). 



