XXIV 



The gland may consist of one cell (unicellular gland), or 

 many lining an inpushing o the surface. 



Wax- and Oil-glands. Functions : to protect from enemies ; 

 to prevent wetting or evaporation ; and to keep the surface 

 supple and lubricated. 



Mucous Glands. Function to lubricate. 



Scent- Glands. Functions: offensive; for recognition ; erotic. 



Sweat-Glands. Function : excreting a watery fluid, whose 

 evaporation cools the body. 



Pigment -Glands. Function: secretion to conceal from 

 enemies. 



Poison-Glands. Functions : defence, offence, and killing 

 prey. 



G. 



LUMINOUS AND ELECTRIC ORGANS. 



Luminous Organs. 

 Plants. 



Many plants show a diffused luminosity varying somewhat in 

 intensity in different regions, but no special organs for the 

 production of light are known. 



Animals. 



In animals the production of light is usually limited to special 

 parts or organs. 



Examples taxonomically arranged. 



Electric Organs. 



Alone present in animals, and are formed by a modification 

 of portion of the muscular and nervous systems. 



Animals. 



Examples taxonomically arranged. 



