On the Structural Constituents of the Nucleus, etc. 447 



portion contains, while the other lacks, the nucleus, the former alone is able 

 to continue to discharge the ordinary vital functions, and to manifest those 

 chemical and physical properties which necessarily underlie them. The 

 enucleated fragment, on the other hand, although it may persist for some 

 time, nevertheless loses, more or less rapidly, all those special faculties which 

 should enable it to maintain a separate existence. Synthetic and secretory 

 activities disappear, and death sooner or later supervenes. 



Seeing, then, that the nucleus plays so fundamental a part in maintaining 

 the due sequence of chemical change in the cell, the question naturally 

 arises as to whether all those properties of the individual which find their 

 expression in form, and in other externally recognisable characters, may not 

 be attributed to the interaction of the nucleus with the cytoplasm external 

 to it ; whether they are not merely the inevitable result and outcome of the 

 series of material changes that succeed each other within the confines of 

 the constituent cells. I believe the answer must be in the affirmative. At 

 the present time, however, such a general statement has but little value 

 beyond expressing the general direction in which the many lines of investiga* 

 tions appear to be advancing. We are not likely, within the near future, to 

 be in a position to trace all the stages which intervene between the importing 

 of raw material and the turning out of the finished fabric. Modern research 

 clearly indicates that the proximate problems are more intricate than they 

 were formerly supposed to be. Nevertheless, I venture to think that the 

 very complexity of the regulatory processes emphasises, rather than 

 diminishes, the probability that a comprehensive physical explanation of 

 organisation and inheritance will one day fall within our reach. But the 

 final synthesis can only be made possible when we have understood the 

 details, when the more immediate problems have been clearly stated and 

 successfully solved. 



Some of these problems are already in process of solution ; thus numerous 

 investigators during the last 30 years have done much to clear up the 

 essential features of fertilisation, although it cannot be said that as yet there 

 exists complete agreement on all points. For while it has been generally 

 conceded since Hertwig's discovery, already alluded to, that the nuclear, and 

 not the cytoplasmic, association constitutes the significant part of the process, 

 there are still some who hold that the fusion of the cytoplasm is of direct 

 and material importance in the transmission of the hereditary properties of 

 the individual. 



As this is a matter of great weight, an examination of the facts yielded by 

 a study of fertilisation is demanded. It is true that the male gamete carries 

 with it into the egg a small amount of cytoplasm. On penetrating the egg, 



