194 ON VAEIABILITY AND ADAPTATION 



gamogenetio variation is included in the nuclear chromatin. 

 That the other constituents of the cell have an influence or can 

 have an influence we do not deny. If in the fertilized ovum the 

 nucleus influences the cytoplasm, so, conversely, the constitution 

 of the cytoplasm must tell upon the nucleoplasm. The facts in 

 our possession indicate that the latter is the subordinate process ; 

 the influence of the nucleus is dominant. This is best indicated 

 by Boveri's remarkable observation that if the nucleus be 

 removed from the sea-urchin's egg and the enucleated mass of 

 cytoplasm be fertilized by the spermatozoon of another species 

 of echinoderm the resultant larva is of the type of the species 

 that afforded the spermatozoon, that is, the nuclear material ; 

 this has conveyed and determined the specific properties of the 

 individual. 



Now, if this be so, it must follow that the nuclear matter 

 controls all the essential cell activities, and this because, studied 

 narrowly, it is seen that the morphological properties of a cell are 

 the expression of the constitution of the cell ; it is the constitution 

 that determines the properties and functions of that cell. All 

 are bound together every whit as much as are the properties of 

 any given salt and the constitution of the same. What is true 

 of the cell holds also of the multicellular individual ; the specific 

 properties of the individual are the summation of the properties 

 of its component cells. If, therefore, nuclear composition dominates 

 the morphology of the individual cell it dominates, likewise, the 

 properties of the individual. 



It must now be asked : What evidence do we possess estab- 

 lishing that this is really the case ? That evidence may be 

 dealt with under many heads. We have to deal with the 

 evidence afforded by : (1) the natural and experimental enuclea- 

 tion of cells ; (2) gross changes observed in the nucleus as the 

 result of cell activities ; (3) the finer changes in the same which 

 may be seen to follow functional activity ; (4) the histological 

 changes in the nucleus associated with morbid conditions ; (5) 

 the chemistry of nuclear and cytoplasmic matter respectively ; 

 and (6) the ferment actions of the cell and their relationship to 

 nuclear activity. 



Let me now lay before you the main data that have been 

 gained under each of these headings, and the conclusions that 

 may reasonably be deduced. 



