DEVELOPMENT OF CELLS. 



125 



which do not form a permanent part of the organism ; such as 

 granulations and cancerous or other malignant growths which 

 undergo a speedy degeneration. (Fig. 64.) 



Fig. 64. 



Fig. 65. 



Cells (and fibres) from encephaloid of tongue, growing rapidly. 



One of the hepatic coeca of 

 the cray-nsh (Astacus affinis), 

 showing the progressive deve- 

 lopment of the secreting cells 

 from the nuclei at its bottom. 

 The stages are shown by the 

 letters a to e. 



The vital force is, as it were, exhausted 

 by this rapid multiplication, so that the cells 

 thus formed are incapable of further deve- 

 lopment, while the slow method by duplica- 

 tion may proceed to any extent. In glandu- 

 lar follicles, however, this rapid multiplication of cells "may often 

 be recognized," for each of the terminal coeca or follicles is regarded 

 as a single parent cell with a persistent nucleus (germinal centre); 

 and it appears that the materials of secretion are eliminated from 

 the blood by the continual development of young cells from this 

 nucleus. (Fig. 65.) 



B. Fissiparous Cell- development, or that by Division. 



In the multiplication of cells by division, the original cell first 



becomes elongated, and two nuclei are developed from the original 



nucleus, by division, apparently, as before described. The cell then 



becomes constricted at the middle, and, the nuclei receding from 



