CELL-LIFE AND CELL-MULTIPLICATION. 259 



nucleus of an ovum is the essential process initiating the 

 development of a new organism, the legitimate inference 

 appeared to be that these two nuclei convey respectively the 

 paternal and maternal traits which are mingled in the off- 

 spring. And when there came to be discerned the karyoki- 

 nesis by which the chromatin is, during cell-fission, exactly 

 halved between the nuclei of the daughter-cells, the conclu- 

 sion was drawn that the chromatin is more especially the 

 agent of inheritance. But though, taken by themselves, the 

 phenomena of fertilization seem to warrant this inference, 

 the inference does not seem congruous with the phenomena 

 of ordinary cell-multiplication phenomena which have noth- 

 ing to do with fertilization and the transmission of here- 

 ditary characters. No explanation is yielded of the fact that 

 ordinary cell-multiplication exhioits an elaborate process for 

 exact halving of the chromatin. Why should this substance 

 be' so carefully portioned out among the cells of tissues which 

 are not even remotely concerned with propagation of the 

 species? If it be said that the end achieved is the convey- 

 ance of paternal and maternal qualities in equal degrees 

 to every tissue; then the reply is that they do not seem to 

 be conveyed in equal degrees. In the offspring there is not 

 a uniform diffusion of the two sets of traits throughout all 

 parts, but an irregular mixture of traits of the one with traits 

 of the other. 



In presence of these two suggested hypotheses and these 

 respective difficulties, may we not suspect that the action of 

 the chromatin is one which in a way fulfils both functions? 

 Let us consider what action may do this. 



7-ie. The chemical composition of chromatin is highly 

 complex, and its complexity, apart from other traits, implies 

 relative instability. This is further implied by the special 

 natures of its components. Various analyses have shown 

 that it consists of an organic acid (which has been called 

 nucleic acid) rich in phosphorus, combined with an albu- 



