THE CELL AND PROTOPLASM. 133 



chromosomes from both parents. It is not yet 

 certain, however, whether the centrosome is a 

 constant part of the cell. In some cells it cannot 

 yet be found, and there are some reasons for be- 

 lieving that it may be formed out of other parts 

 of the cell. The nucleus is always a direct de- 

 scendant from the nucleus of pre-existing cells, 

 so that there is an absolute continuity of descent 

 between the nucleii of the cells of an individual 

 and those of its antecedents back for numberless 

 generations. It is not certain that there is any 

 such continuity of descent in the case of the 

 centrosomes ; for, while in the process of fertiliza- 

 tion the centrosome is handed down from parent 

 to child, there are some reasons for believing 

 that it may disappear in subsequent cells, and 

 later be redeveloped out of other parts. The 

 only part of the cell in which complete continuity 

 from parent to child is demonstrated, is the 

 nucleus and particularly the chromosomes. All 

 of these facts simply emphasize the importance 

 of the chromosomes, and tell us that these bodies 

 must be regarded as containing the most import- 

 ant features of the cell which constitute its 

 individuality. 



WHAT IS PROTOPLASM 1 



Enough has now been given of disclosures of 

 the modern microscope to show that our old 

 friend Protoplasm has assumed an entirely new 

 guise, if indeed it has not disappeared altogether. 

 These simplest life processes are so marvellous 

 and involve the action of such an intricate mass 

 of machinery that we can no longer retain our 



