DEVELOPMENT OF CELLS. 



123 



first is the parent ; while the nucleolus bears the same relation to 

 the nucleus that the last does to the original cell, i. e. it is to be de- 

 Fig. 60. 



Fig. 61. 



Endogenous cell-development. A, B, c, D. Early stages of the process (ovum of Ascaris dentata). 

 E, F, a, H. More advanced stages (ovum of GucuUanus elegans). 



veloped into the third generation the cell of which the second is 

 the parent. While the nucleus is forming, it develops within itself 

 the nucleolus; and while it is 

 becoming the second - genera- 

 tion cell, the nucleolus becomes 

 a nucleus, and, in its turn, forms 

 a nucleolus within itself. Thus 

 the nucleus itself becomes the 

 next cell, though it is not here 

 asserted that it in no case forms 

 a cell around itself. Hence, also, 

 if a cell has never contained a 

 nucleus, it is itself called a free 

 nucleus, as we have seen, or an 

 elementary vesicle. It is not, 

 physiologically, a cell, and has 

 no power of multiplication. 



Such are the corpuscles of tu- 

 bercle, and the Colored COrpUS- Endogenous cell-growth (meliceritious tumor). 



cles of the blood (p. 115). These " Cells with nuclei variollsl y Developed. 6. p a - 



J m rent cell filled with young cells, which have ori- 



Or may not Contain nU- ginatea from the granules of the nucleus. 



