10 



THE PHENOMENA OF LIFE 



of lymphatic glands, and in some small nerve cells. Their position in the cell 

 is very variable. -In many cells, especially where active growth is progressing, 

 two or more nuclei are present. 



Cell Division and Growth. The division of a cell is preceded by 

 division of its nucleus, which may be either direct or indirect. Direct or simple 

 division, amitosis or akinesis, see figure 10, occurs without any change in the 

 arrangement of the intranuclear network. A constriction develops at the cen- 

 ter of the nucleus, possibly preceded by division of the nucleoli, and gradually 

 divides it into two equal daughter nuclei. A similar constriction of the pro- 

 toplasm of the cell occurs between the daughter nuclei and divides it into two 

 parts. 



Indirect division, mitosis, or karyokinesis is the usual method, and consists 

 of a series of changes in the arrangement of the intranuclear network, resulting 



a 



FIG. 10. Akinesis, Amitosis, or Direct Cell Division. A, Constriction of nucleus; B, division 

 of nucleus and constriction of cell body; C, daughter nuclei still connected by a thread, division 

 being delayed; D, division of cell body nearly complete. (After Arnold.) 



in the exact division of the chromatic fibers into two parts, which form the 

 chromoplasm of the daughter nuclei. The changes follow a closely similar 

 course in both plant and animal cells. 



Differences between Animals and Plants. Having considered at 

 some length the vital properties of protoplasm, as shown in cells of animal 

 as well as of vegetable organisms, we are now in a position to discuss the ques- 

 tion of the differences between plants and animals. It might at the outset 

 of our inquiry have seemed an unnecessary thing to recount the distinctions 

 which exist between an animal and a vegetable as they are in many cases so 

 obvious, but, however great the differences may be between the higher animals 

 and plants, in the lowest of them the distinctions are much less plain. 



In the first place, it is important to lay stress upon the differences between 

 vegetable and animal cells, first as regards their structures and next as re- 

 gards their functions. 



