KARYOKINESIS 



usually presents one or more vacuoles. The uses and properties of 

 these various parts will appear in the study of karyokinesis (mitosis), 

 or indirect cell-division ; and the structures just described are observed 

 in what is known as the " resting " cell. 



All animal tissues, organs and systems are composed of cells derived 

 originally from a single female cell, the ovum, fertilized by union with 

 a male cell, and are produced by indirect cell-division. " It has been 

 estimated that the number of cells entering into the composition of 

 the body of an adult human being is about 26, 500,000, 000,000,000 " 



Attraction -sphere enclosing two centrosomes. 



Nucleus { 



Plasmosome, or 



true 



nucleolus 



Chromatin- 



network 



Linin-network 



Karyosome, 

 net-knot, or 

 chromatin- 

 nucleolus 



Plastids lying in the 

 cytoplasm 



Vacuolc 



Passive bodies (meta- 

 plasm or paraplasm) 

 suspended in the cy- 

 toplasmic meshwork 



Fig. 2. Dingram of a Cell (Wilson). 



Its basis consists of a thread-work (mitome, or reticulum) composed of minute granules (micro- 

 somes) and traversing a transparent ground-substance. 



(McMurrich). In the adult the cells appropriate different substances, 

 organic and inorganic, become specialized and are arranged into differ- 

 ent tissues and organs possessing varied functions. The one function 

 or property, however, which all cells have in common, is that of assimi- 

 lating nutritive matters to supply loss by the constant changes charac- 

 teristic of living structures. The changes that involve the breaking down 

 of living substance are known as katabolic. The process of repair is 

 called anabolism. 



KARYOKINESIS (MITOSIS) 



Prophases. Indirect cell-division begins with a separation of the 

 attraction-sphere into two, each one carrying a centrosome, or polar 



