78 



THE STORY OF LIFE'S MECHANISM. 



four, and by repeated divisions of this kind there 

 arises a solid mass of smaller cells (Fig. 8, b to /), 

 called the mulberry stage, from its resemblance 

 to a berry. This is, of course, simply a mass of 

 cells, each derived by division from the original. 

 As the cells increase in number, the mass also 

 increases in size by the absorption of nutriment, 

 and the cells continue dividing until the mass 

 contains thousands of cells. Meantime the body 



a 



FIG. 8. Successive stages in the division of the developing egg. 



of the animal is formed out of these cells, and 

 when it is adult it consists of millions of cells, all 

 of which have been derived by division from the 

 original cell. In such a history each cell comes 

 from pre-existing cells and a cytoblastema plays 

 no part. 



It was impossible, however, for Barry or any 

 other person to follow the successive divisions of 

 the egg cell through all the stages to the adult. 

 The divisions can be followed for a short time 

 under the microscope, but the rest must be a 



