lOO BIOLOGICAL LECTURES. 



others believe ,that the influence of the nucleus upon the 

 cytoplasm is that of a fermentative action. To a fourth group 

 of investigators, {e.g., Verworn), again, the action of nucleus 

 and of cytoplasm is a reciprocal one, the nucleus influencing 

 the cytoplasm, and the cytoplasm influencing the nucleus in 

 return, by the interchange of the metabolic products. This 

 last view is adopted in the present paper. The results of 

 operations performed on the nucleated cell seem best to 

 support this view. 



All of these explanations are finally reduceable to two funda- 

 mentally different views one may take in regard to the nature 

 of chromosome and cytoplasm in each cell. Some hold {a) that 

 the nucleus and cytoplasm are essentially one and the same 

 substance, and that they only differ from each other, in so 

 far as their stages of development are concerned. Hence the 

 difference between the nucleus and the cytoplasm is merely 

 that of degree. Others, on the other hand, maintain (/;) that 

 the difference between the nucleus and the cytoplasm is not 

 that of a degree of development of one and the same substance, 

 but of the kind of material of which each is composed. 



So far as we can judge from the micro-chemical reactions 

 of nucleus and cytoplasm, they must be regarded as belonging 

 to two substances entirely different from each other. There 

 is no evidence to show that one is actually produced from the 

 other, but the cytoplasm always originates from the preced- 

 ing cytoplasm, and the nucleus always from the preceding 

 nucleus. 



There are, then, four well ascertained facts, in regard to 

 the nature of nucleus and cytoplasm ; viz., 



1. The two elements in each cell — the chromosome and 

 the cytoplasm — have the capacity for assimilation, growth and 

 multiplication by division. 



2. Each is essential to the physiological existence of the 

 other. 



3. The chromosome always originates from the preceding 

 chromosome, and the cytoplasm from the preceding cytoplasm. 



4. Each has a definite micro-chemical reaction, different 

 from the other, and is composed of different chemical substance. 



