108 THE STORY OF LIFE'S MECHANISM. 



long. Facts like these demonstrate conclusively 

 the vital importance of the nucleus in cell activ- 

 ity, and show us that the cell, with its power of 

 continued life, must be regarded as a combina- 

 tion of proto- 

 plasm with its 

 nucleus, and 

 cannot exist 

 without it. It 

 is not proto- 

 plasm, but cell 

 substance, plus 

 cell nucleus, 

 which forms 

 the simplest 

 basis of life. 



As more 

 careful study 

 of protoplasm 

 was made it 

 soon became 

 evident that 

 there is a very 

 decided dif- 

 ference be- 

 tween the nu- 



FIG. 25. A cell cut into three pieces, only one 

 of which, No. 2, contains any nucleus. 

 This fragment soon acquires the original 

 form and continues its life indefinitely, as 

 *hown at B. The other two pieces though 

 living for a time, die without reproducing. 



cleus and the 

 protoplasm. 

 The old statement that the nucleus is simply 

 a bit of dense protoplasm is not true. In its 

 chemical and physical composition as well as 

 in its activities the nucleus shows itself to be 

 entirely different from the protoplasm. It con- 

 tains certain definite bodies not found in the 



