98 Introductory Biology 



well as its individuality. Organisms which possess such an organization 

 are said to possess axiate organization. This phenomenon is studied in 

 various organisms in other chapters. 



VIII. REGENERATION 



The protoplasms of all li\ing organisms have the ability to regenerate 

 to a greater or lesser degree (Fig. 28). If certain parts of an organism 

 are destroyed or impaired, there is an attempt on the part of the indi- 

 vidual to regain its completeness and normality. 



Fig. 28. — Regeneration of animals as shown by A, Hydra; B, Planaria; C, star- 

 fish: D, earthworm. The Hnes show the position where the parts were removed 

 and the darker (stippled) areas are those which have been regenerated. Note 

 that in the starfish the missing ray is regenerated and the missing ray also re- 

 generates the four missing rays. The kind of regeneration which develops depends 

 to a great extent upon where the cut is made. 



In general, regeneration in the higher or more complex organisms is 

 more or less limited to certain structures and regions. If the skin on the 

 tip of a human finger is lost, it will be replaced, but if the tip of the 

 entire finger is removed, there is no appreciable restoration of the lost 

 part. Regeneration thus is relative and is determined or influenced by 

 the part aflfected. Other illustrations of regeneration of higher organ- 

 isms are: the healing of wounds of plants and animals, repair of broken 

 bones, production of new blood corpuscles, replacement of sap lost from 

 injured plants, and renewal of bark removed from trees. 



