220 ORIGIN AND NATURE OF LIFE 



treated with stains, it reacts differently from 

 the rest with these chemical substances. 

 A stain which unites strongly with this part 

 usually only stains the other parts lightly 

 or not at all, and a different stain may behave 

 in exactly the reverse manner. This view 

 is confirmed when many other different types 

 of cell than the amoeba are subjected to 

 chemical examination. Every complete and 

 perfect living cell possesses one, or more, 

 of these structures, and it has most important 

 relationships to the processes of cell-reproduc- 

 tion and growth. This part of the cell is 

 called the nucleus, and it is the central part 

 of the whole. When a cell is injured, or 

 mechanically divided, the portion attached 

 to the nucleus, even if it be the smaller part, 

 usually recovers and reproduces a whole cell 

 again, but a part containing no nucleus, 

 or portion of a nucleus, perishes like a 

 branch cut off from a tree. Remarkable 

 changes in the nucleus precede the processes 

 of reproduction in the cell when one cell is 

 about to form two. Before reproduction 

 commences, the nucleus possesses a reticulate 

 or a sponge-like structure, but at a certain 

 stage in the cell-life, some chemical alteration 

 due to a heaping up of energy, causes this 

 structure to alter spontaneously. The peculiar 



