248 SOME ASPECTS OF CELL-CHEMISTRY AND CELL-PHYSIOLOGY 



B. PHYSIOLOGICAL RELATIONS OF NUCLEUS AND CYTOPLASM 



How nearly the foregoing facts bear on the problem of the form- 

 ative power of the cell in a morphological sense is obvious, and they 

 have in a measure anticipated certain conclusions regarding the role of 

 nucleus and cytoplasm which we may now examine from a somewhat 

 different point of view. 



Briicke long ago drew a clear distinction between the chemical and 

 molecular composition of organic substances, on the one hand, and, 

 on the other hand, their definite grouping in the cell by which arises 

 organization in a morphological sense. Claude Bernard, in like man- 

 ner, distinguished between chemical synthesis, through which organic 

 matters are formed, and morphological synthesis > by which they are 

 built into a specifically organized fabric ; but he insisted that these two 

 processes are but different phases or degrees of the same phenome- 

 non, and that both are expressions of the nuclear activity. We have 

 now to consider some of the evidence that the formative power of the 

 cell, in a morphological sense, centres in the nucleus, and that this is 

 therefore to be regarded as the especial organ of inheritance. This 

 evidence is mainly derived from the comparison of nucleated and 

 non-nucleated masses of protoplasm ; from the form, position and 

 movements of the nucleus in actively growing or metabolizing cells ; 

 and from the history of the nucleus in mitotic cell-division, in fer- 

 tilization, and in maturation. 



i. Experiments on Unicellular Organisms 



Brandt ('77) long since observed that enucleated fragments of 

 Actinosph&rium soon die, while nucleated fragments heal their wounds 

 and continue to live. The first decisive comparison between nucle- 

 ated and non-nucleated masses of protoplasm was, however, made by 

 Moritz Nussbaum in 1884 in the case of an infusorian, Oxytricha. 

 If one of these animals be cut into two pieces, the subsequent 

 behaviour of the two fragments depends on the presence or absence 

 of the nucleus or a nuclear fragment. The nucleated fragments 

 quickly heal the wound, regenerate the missing portions, and thus 

 produce a perfect animal. On the other hand, enucleated fragments, 

 consisting of cytoplasm only, quickly perish. Nussbaum therefore 

 drew the conclusion that the nucleus is indispensable for the forma- 

 tive energy of the cell. The experiment was soon after repeated by 

 Gruber ('85) in the case of Stentor, another infusorian, and with the 

 same result (Fig. 1 12). Fragments possessing a large fragment of the 

 nucleus completely regenerated within twenty-four hours. If the nu- 



